Hepworth HDPE Drainage


Product and Technical Guide



Hepworth PME Introduction

7 6 7 7 9 9

Wavin Introduction





- Domestic waste water


Principles of waste water discharge 2.1 General design principles

- Overpressures and underpressures - Primary discharge system - Secondary discharge system - Restricted secondary discharge system - Air admittance valves - Direct separated discharge system - Balancing lines

2.2 Filling of pipework

10 10 11 12 12 12 12 13

2.3 Fall

2.4 Access fittings


Peripheral requirements for removal of waste water

3.1 Traps

3.2 Connecting pipes 3.3 Collecting pipes

3.3.1 General requirements

3.3.2 Connections to collecting pipes 14 3.3.3 Connection separations and sequence 16

3.4 Stacks


3.4.1 Connections to stacks


- Method 3.4.2 Angled sections

17 3.4.3 Stack foot and connection-free zones 17 3.4.4 Stack diameter 18

3.5 Underground pipes 3.6 Ventilation pipes 3.7 Roof penetrations

18 18 19 19 20 21 21 21 22 22

3.8 Discharge of waste water Dimensioning for waste water

4 5


5.1 The generation of noise

5.2 Noise transmission

5.3 Noise reducing measures

5.4 Fittings



Casting in heat cured concrete and extrusion shrinkage 23





23 23

At both its purpose-built facility in Dubai and on site, training covering the proper installation and use of the range of products is provided to customer’s technicians. Here they are instructed in using best-practice techniques for jointing of the various piping materials, correct installation of fittings and accessories and operation and maintenance of their systems. Following successful completion of such training courses the technicians will become certified installers of those HEPWORTH PME ( LLC ) products covered in the course. The benefits of this training are enormous because incorrectly installed systems will certainly fail prematurely at substantial cost to the owner or operator, particularly on those systems that are installed underground or with difficult access. To complement the range of items manufactured in Dubai, HEPWORTH PME ( LLC ) also represents a select group of international manufacturers who further enhance the scope of supply to accommodate other aspects of water and gas flow management. Encompassing diverse fields such as irrigation to fire-fighting and district cooling to domestic water supply, complete systems and individual components can be sourced from one professional outlet conveniently located to serve the needs of the specifier or contractor. HEPWORTH PME have a licensing and manufacturing agreement with Wavin to produce the pipes in Dubai. The fittings will be supplied from Wavin overseas. The pipes are manufactured to EN 1519 specifications which incorporate a test temperature of 110 o C.

HEPWORTH PME ( LLC ) is the region’s premier manufacturer and supplier of a comprehensive range of high quality plastic pipes, fittings and accessories used for the distribution and transmission of water, wastewater and gas. Established in Dubai for well over three decades and represented by a chain of branch offices throughout the area HEPWORTH PME ( LLC ) are able to satisfy the requirements of the industry professionals from its substantial stock holding of products conforming to the various international standards in common use in the Middle East. The demand for readily available high quality pipes and fittings prompted HEPWORTH PME ( LLC ) to establish a modern manufacturing facility in Dubai back in 1991. Using the latest equipment and techniques the company produces PVC-U, Polyethylene and GRP pipes in a wide range of diameters. Following further investment in 1999 injection moulding machines were introduced to produce PVC-U, polyethylene and polypropylene fittings. In addition to this fabrication of standard, specialized and bespoke fittings using PVC-U, ABS, PPR, polypropylene and polyethylene is undertaken to provide solutions for the discerning water engineer. Being the first company of its kind to achieve BS Kitemarks and ISO 9002 accreditation in the region, they are now designated as an ISO 9001:2000 accredited manufacturer. Quality is therefore paramount and this is reflected by the fact that HEPWORTH PME ( LLC ) holds BS Kitemark licences covering 109 of the locally produced products. We also have FM approval for polyethylene pipe underground fire fighting equipments. Optimum performance and longevity is further assured by the company’s commitment to customer training.

7.1 Design

7.1.1 Fixings - HDPE 7.1.2 Brackets


- support bracket - clamping bracket - fixed point bracket 7.1.3 Freely suspended pipework


- temperature differences • cold pipework • warm pipework • hot pipework

7.2 Installation methods

24 25

7.2.1 Flexible installation

- flexible installation with expansion sleeves and couplers - flexible installation with flexible connectors - bracket separations for flexible installation - bracket distribution for flexible installation

7.2.2 Rigid installation (HDPE)


- brackets and bracket separations for rigid installation

7.2.3 Cast-in pipework

29 31



8.1 General

31 8.1.1 Pipework in the waste removal system 31 8.1.2 Fixing equipment (brackets) 31 8.1.3 Storage 31 8.1.4 Oval pipe ends 31 8.1.5 Shortening pipes 31

8.2 Brackets

31 31

8.2.2 Joints in HDPE

- butt welding - electro-weld sockets - electrical spigot welding - preparation work - welding procedure - use of non-standard pipe - rubber seals - expansion sockets


Situations during construction

35 36 37 38



10 11 12

Pressure testing


Product list

1. General


purpose the rainwater may also be used for flushing toilets, washing clothes or cleaning purposes. In that case the rainwater is stored in a tank which must be provided with an overflow. Before proceeding to investigate the principles of drainage it will be as well to determine the nature and quantity of the drainage requirements.

charges of varying kinds, temperatures, quantities, frequencies and so on. On health, hygiene and odour control consi- derations the system is sealed with traps or siphons. When discharges take place, air in the system has to make way (ven- ted) for waste water. The principal problems of drainage are as follows: intermittent drainage, enclosed open system, complete removal of soil and water is required. Excess rainwater is also led away to the external sewer, nowadays generally to a separate storm drain. If the water is relatively clean it may be led from the storm drain to balancing ponds or waterways. Alternatively, clean rainwater may also be discharged onto the land around the property or into a collective facility. Where the roof is suitable for the

Water is supplied by means of enclosed pipework systems using internal pres- sure. Waste water is generated when the supplied water is used for cleaning, was- hing, cooking and for flushing away human waste. In discussing waste water a distinction is made between black water (from toilets) and grey water (from washing machines, showers and similar). The black water presents a direct hazard to health, grey water does not. Black and grey water are generally discharged together into the above-ground drainage system which carries the water to the underground private sewer (U-drain) into the public sewer or local treatment facility (septic tank). The above-ground drainage system is an open system which is accessible at several locations for dis- The system is manufactured to EN 1519 specifications which incorporate a test temperature of 110 o C.

Wavin HDPE Product & Technical Guide


This technical manual on HDPE above-ground drainage systems deals with the removal of domestic waste water and rainwater from houses and residential and commercial properties using plastic piping systems. It covers all aspects from design to installation. The manual is intended for clients, architects, construction specialists, building co-operatives, building inspectors and of course for installers. If you have any questions, wishes or practical problems not covered by this manual then we would ask you to submit them to us together with any suggestions for amendments and additions. Since our systems are often utilised in circumstances beyond our control, we cannot accept liability for the consequences of applying the information provided in this manual.

The Wavin group of companies is one ofthe largest manufactur- ers of complete plastic pipe systems for the Building, Civil and Utility markets in Europe. In addition to having its own produc- tion facilities in almost every country on the European continent, Wavin also participates in the equity of plastic pipe companies in Australia, New Zealand and Singapore. In the remainder of the world the company is proud of an ever increasing impressive network of licensees, distributors and agents. Wavin has manufac- tured and supplied plastic pipe systems since 1955.The strength of the Wavin Group in terms of manufacturing capability and technical resources places the company at the forefront of the industry for product quality, innovation, technical support and customer service. A survey carried out by international consultants for European Plastic News, a leading trade journal, identified Wavin as the foremost contributor in the development of plastic pipe systems and the leader in the field of marketing and technology.

1.1 Quantities

Domestic waste water The quantities of water consumed and requiring removal vary appreciably throughout the day and depending on the source of the discharge. 120 to 130 litres per person per day are used as the basis of calculations for supplies required for domestic use. The assumption is that the water used will be led off at the rate of 10 to 12 litres per person per hour. Illustration 1.1 shows the discharge pat- tern for a 3 to 4 person household over 24 hours. Basic discharge rates (Q¡) to determine the required capacity for a given section of pipework are included in NEN 3215 (see illustration 1.2). Illustration 1.2 also shows the required diameters for the trap and for the pipe connecting to the source of the discharge. The quantity of waste water in collecting pipe stacks, that is, those containing discharges from several fittings, can be determined by means of the formula: Q o = p Σ Q ¡ , where Q o and Q ¡ are in l/s. Σ Q ¡ is the sum of the baseline discharge rates to be removed by a collecting pipe. p is a coefficient for simultaneity: - houses and residential properties p = 0,5 - schools, offices, hotels, restaurants, hospitals p = 0,7 - laboratories, sustained industrial discharges p = 1,2 - commercial kitchens p = 1,4

Wavin Overseas

Wavin Overseas B.V., situated in The Netherlands, is the central export organisation of the Wavin Group dedicated to providing a global service. HDPE Fittings are Manufactured in Italy. Wavin Overseas sells Wavin products, supplies technology (under licence) and equipment to manufacture these products locally. Wavin Overseas is experienced in setting up complete factories, delivering a comprehensive package of manufac turing equipment, ancillaries and services such as production know-how and technical support. In effect Wavin Overseas can supply all the help you need to supply your market. Wavin Overseas operates under a Quality Management System, which is accredited to EN ISO 9001:2000 by the Dutch Council for Accreditation.

A Wide Range of Products

Wavin’s extensive range of plastic pipe systems is designed and manufactured to meet the highest standards set by the building and construction industry worldwide. Wavin’s products are generally available ex-stock from one of our numerous distri-bu- tors around the world.


41 l/pp.day 33 l/pp.day 20 l/pp.day 17 l/pp.day 9 l/pp.day 120 l/pp.day

Illus. 1.1 Mean water consumption for an average household over 24 hours.


Washing machine






Product list

2. Principles of waste water discharge

cause compression of air, and overpres- sures and underpressures will be created. These must be kept within limits. Steps must also be taken to prevent excessive overpressures or underpressures created by hydraulic sealing, whereby little or no air can pass over or through a flowing mass of water. The principles and stipula- tions for the removal of waste water are based upon these assumptions. Having dealt with general construction principles,

In houses and other residential properties waste water and rainwater must be collected separately and led to the exterior of the building, or at least up to the location of a discharge construction for the rainwater. It is important in removing waste water that the pipework empties thoroughly, that any soil is carried along by the water and that no waste water or sewer gases enter the building via the trap. Discharges will

this chapter goes on to discuss the waste water system from the fitting to the building boundary. Requirements and problems are examined and solutions suggested.



diameter of

external diameter connecting pipe in PVC and PE

reduced external diameter for wall and floor piping

discharge l/s trap

(pipe type)



(mm) 1)

mouthwash unit drinking fontain leakage removal overflow hopper hand washbasin washbasin





2.1 General design principles




In order to prevent traps being emptied by suction or pressure, overpressures and underpressures must not exceed 300 Pa (30 mm water column). Air must be able to escape from the system (venting) and to enter the system (admittance). A ventilated discharge pipe is used for this purpose. Good practice is to create a primary discharge system extending the discharge stack above roof level (see illustration 2.1). This system allows air to continually enter and vent from the main sewer. In the case of a secondary discharge system, each fitting or branch pipe is connected to a separa- te ventilation system. A secondary dis- charge system may be taken through the roof or connected to a primary discharge system prior to this being taken through the roof (illustration 2.2). An unavoidably long branch pipe may give rise to pro- blems in a primary system. The section of the branch pipe furthest from the stack may then be connected to a restricted secondary discharge pipe. This may either be led directly through the roof or connected to the stack or to the primary discharge stack. This may be referred to as a circulating or end discharge system (illustration 2.3). In this case an internal air admittance vent on the end of the branch pipe may be useful. However these can only admit air to the system, not release it. Where overpressure occurs in the system a membrane is pressed closed, otherwise sewer stench would enter the room. The air admittance surface area must be as close as possible to the cross sectional area of the collection stack. For ease of maintenance the air admittance vent must be fitted in accessible place

shower without tray bidet automatic washing machine domestic dishwasher urinal footbath kitchen sink (single or double)




slop sink


or 75



shower with tray



sink with capacity over 30 l Toilet





siphonic closet





bedpan sluice floor drain 32 mm




40 50 50

40 mm 50 mm 70 mm 100 mm


- - - -

63/75 63/75

1,0 1,5 2,0


- -


1) reduction permissible if • total length of connecting pipework is no more than 3,5 m. • length of wall-mounted pipe (horizontal) is no more than 0,5 m and only a single vertical element is not longer than 1,5 m.

15 20 25 30 40 50


9 8 7 6 5 4

Illus. 1.2 Baseline discharge, required

diameter for traps and (reduced) connecting pipework for a variety of fittings.



2 2,5


1,0 0,9 0,8 0,7 0,6 0,5 0,4

Q o can be read off for different values of p in illustration 1.3 if the sum of Q ¡ is known. Q o may never be lower than the highest value for baseline discharge rates.

1 1,5

2 3 4 5 6 7 8 910


20 30 40 50 70 100 150 200 300 400500 700 1000

Q i (sum of baseline discharge (l/s) Q o may never be less than the largest of the baseline discharges

Illus. 1.3. Relationship between Q o , p and Q i . Example: Calculated using table in 2 gives Q i = 52 l/s Office (p = 0,7) hence Q o = 5 l/s

Illus. 2.1 Principles of the primary discharge system.



Principles of waste water discharge

Principles of waste water discharge

Stacks can often be cleaned from the roof provided the vent cap can be removed. With high buildings it is recommended that an access fitting be provided every 3 to 4 storeys. Ventilation lines, including secondary ventilation, may become (partly) blocked when rainwater gets in or by deposition of dry matter from the environment. Vent lines should therefore also be provided with access fittings.

water flowing away too quickly, which can give rise to hydraulic sealing.

Equal discharge and flow are assumed. This will not be the case immediately downstream of the fittings, but the wave of water will be equal after some time (and some length of pipe) has passed. 2.3 Fall A certain flow rate is required to correctly remove foul water. A lower limit of 1:200 has been established for this purpose. 1:400 or 1:500 may be possible with shorter runs, on condition that a calcula- tion is provided. In practice the installa- tion will then have to be carried out with great care. Further, any hydraulic distur- bances must be minimised: a fitting upstream that is frequently used and/or has a fairly large baseline discharge is an advantage in this case. In general a maxi- mum fall of 1:50 is maintained to prevent

above the level of the fittings. An air admittance valve may also be useful in solving problems associated with sepa- rate discharging fittings. However they cannot take the place of the (primary) vent pipe. A separate direct discharge system (or direct parallel discharge system) may be employed to solve problems where addi- tional fittings are connected to an existing system. This may facilitate air movement, while hydraulic sealing has less effect and the capacity of the stack may increase. Such a discharge pipe will be connected exclusively to the stack, that is, no branch pipe will be connected (illustration 2.4). In places in the system where hydraulic sealing may be caused occur because of bends, transitions from vertical to horizontal or where insufficient

airflow is possible, a balancing line may be provided. This line allows the balan- cing of overpressures and underpres- sures. One common example arises if the stack is not fully vertical but has horizontal sections (illustration 2.5). The uppermost example, a restricted secon- dary discharge system, is the most common solution. The recommendations in this manual are based upon the presence of a primary discharge system. 2.2 Filling of pipework In order to allow a free flow of air the pipework must be designed to take account of the quantities to be removed, the fall (= gradient or hydraulic slope) and the diameter, so that the pipes are no more than 70% full (water depth is 0.7 x the internal pipe diameter).

2.4 Access fittings Blockages may occur even in well-

designed discharge systems, for example as a result of deposits (e.g. solidified fat) or improper use of the drain (paint residu- es, food remnants, cat litter, potting com- post, small objects, etc). Access fittings should therefore be provided at strategic locations in the pipework, taking account of the fact that clearing equipment can only cope with limited changes in direc- tion. Access fittings should be easily accessible and placed in such way that hoses or springs can easily be inserted. The access fitting should where possible be located on top of the pipe so that in the case of blockages the whole pipe does not empty if the cap is removed.

Acces Fitting


Illus. 2.4 Principles of the direct separate discharge system (the stack discharges directly).

Illus. 2.5 Examples of balancing pipework.

Illus. 2.2 Principles of secondary discharge system.

Illus. 2.3 Example of restricted secondary discharge system.



The uppermost method is most commonly applied.

Peripheral requirements for removal of waste water

3. Peripheral requirements for removal of waste water

As well as proper calculation and selec- tion of the appropriate diameter, a num- ber of other factors are important to achieve good operation and prevent hydraulic seals, fouling of pipes and excessive overpressures and under- pressures. This chapter deals with these peripheral requirements. For this purpose we now follow the pipework from the source of the discharge onwards. 3.1 Traps Each discharging fitting must be provided with a trap. A certain diameter will be required, depending on the baseline discharge level (see illustration 1.2). If too small a diameter is chosen then emptying of the fitting will take too long. Self- siphoning (emptying of the trap through suction when the fitting is discharged) may occur, and noise will increase. On the other hand, an excessive diameter will lead to a lower speed of flow. This results in greater difficulty in carrying away soiling and blockages may result. There must be at least 50 mm of water (500 Pa) in a trap. The seal will remain intact if a maximum underpressure of 300 Pa arises in the system, even if some of the water in the trap has evaporated. Traps with rubber seals are to be preferred because of easier cleansing and replacement. This also prevents problems arising from the use of different materials. There are two main types of trap, the tubular (M,D,P,S types) and the bottle type (which includes floor-mounted varie- ties). Each type has its advantages and disadvantages. The bottle types are more readily blocked, but also more easily cleared. The bottle types lose less water to evaporation and are less sensitive to pressure differences (there is more water to be put into motion). A tubular trap is less prone to blocking because the speed of flow is higher and the shape allows free flow.

ted using a connecting pipe. During discharge the connecting pipe must be completely filled with water. No require- ments are therefore set down for the minimum fall. Some fall is certainly requi- red however as the pipe must empty fully. If the pipe is completely filled a plug of water is created which can cause under- pressure. This empties the trap by suc- tion and gives rise to gurgling sounds (illustration 3.1). Complete filling of the pipe must therefore make way as rapidly as possible for partial filling. Significant here are the length of the connecting pipe, its diameter, whether the pipe runs vertically or horizontally and the number of changes in direction. The required dia- meter is stated in illustration 1.2. If the total length of the connecting pipework from the trap to the common stack is greater than 3.5 metres then a diameter required for the excess must be determi- ned as if it were a collecting stack, using 3.3 and illustration 4.1. The total length of a connecting section may not exceed 12 metres. The diameters of parts a and b in illustration 3.2 may be smaller provided the following conditions are met: total length less than 3.5 metres

3.3.1 General

Additionally, the maximum permitted sum of changes in direction is 135°. Where these conditions are met the flushed contents of the pan can reach the vertical stack or under- ground pipe in one go and blockages and deposits are prevented. Length is taken to mean the horizontal length from the toilet to the vertical stack or underground pipe. All reductions in the collecting pipe must be eccentric (top of pipe at a single level).

requirements The diameter must be determined on a section by section basis (from connecting section to connecting section). Collecting pipes must be as straight and as short as possible. Bends must not be tighter than 45°. To prevent soil being left behind, the maximum sum of changes in direction depends on the fall (illustra- tion 3.3). If the sum of changes in direction is larger, the next largest diameter should be selected for the extra length, unless discharge takes place upstream. For a section with no toilet, the maxi- mum length may be 12 metres, if two fittings are connected, where the Q¡ for one of these is no greater than 0.5 l/s (illustration 3.4). For a section including a toilet and other fittings with Q¡ less than 0.75 l/s, the permitted maximum length is dependent on the fall (illustration 3.4).

a < 0,5 m b < 1,5 m; if b > 1,5 m calculate as a stack

a + b + c < 3,5 m; if > 3,5 m calculate as a collecting pipe

Illus. 3.2 Conditions for reduction in

diameter of a connecting pipe, see also illustration 1.2.

part a less than 0.5 metres part b less than 1.5 metres (total of the vertical sections).

Illus. 3.1 Self-siphoning or suction emptying of the trap.

The diameter thereby permitted is stated in illustration 1.2. In view of the possibility of damage and for maintenance it is recommended that a rubber sleeve should be used in the floor (at location x). 3.3 Collecting pipes Many different factors may affect collec- ting pipes. This accounts for the many conditions set down to achieve the problem-free removal of waste water. These requirements serve two main aims: To ensure that free-flowing air remains available above the water. To ensure that no fouling takes place.



max sum of changes of direction

example: 1:200 section d larger Ø 1:150 section d larger Ø

1:50 1:75

1:75 1:100 1:140 1:180

221/2 °


1:100 1:140 1:180

671/2 °

1:100 section c en d larger Ø 1:50 section b,c en d larger Ø


1:200 1121/2 ° Where these limits are exceeded, the next diameter up should be selected for the extra length, unless discharge takes place upstream.

3.2 Connecting pipes Every fitting must be separately connec-

Illus. 3.3 Maximum permissible sum of changes of direction for a particular fall in collecting pipes.



Peripheral requirements for removal of waste water

Peripheral requirements for removal of waste water

3.3.2 Connections to

toilets and other

maximum maximum permissible

collecting pipes



sum of changes of direction

toilet only

Horizontal connections must be made with 45° T-pieces. Side connections: All reductions at horizontal connec- tions of connecting pipe sections to the collecting pipe must be eccentric. The upper surfaces of the pipes must be at a single level so that air can continue to flow and soiling can not flow back (illustration 3.5). If eccentric reducing T-pieces were available they would have to be provided in left and right handed models. In practice a piece with equal diameters is used with an eccentric reducing piece inserted in the appropriate side. N.B. a "running" reducer is better from a hydraulic perspective and makes less noise than an inserted reducer does. Oblique connections: Reducing T-pieces may be used with oblique connections provided the angle with the horizontal is between 30° and 45° (illustration 3.6). This connection is acceptable from a hydraulic viewpoint as the water flow in the collecting pipe is not unduly disturbed by the entry of the flow of water. This is a good solution to pre- vent foul water flowing back from the

3,5 m


(=connection pipe) toilet only


(calculated as collecting pipe)

1:50 ; 12 m 1:100 ; 8 m 1:200 ; 5 m



toilet + fitting Q i < 0,75 l/s toilet + fitting Q i 0,75 l/s

no restrictions

see illustration 3.3

(i.e. 2 or more toilets) 1 fitting no toilet (= connecting pipe) 1 fitting no toilet

3,5 m


Illus. 3.5 Horizontal connection to collecting pipe with eccentric reducer.

Horizontal collecting pipe 45° reducing T-piece with connec- ting pipe between 30°and 45° with horizontal section < 30° as in illustration 3.5. > 45° conditions as in illustration 3.7

12 m

see illustration 3.3

(calculated as collecting pipe) 2 fittings no toilet

12 m

see illustration 3.3

where one Q i < 0,5 l/s 2 fittings no toilet

no limitations

see illustration 3.3

Illus.3.6 Oblique connection.

both Q 0,5 l/s * applies for length of toilet connecting pipe + length of collecting pipe

Illus. 3.4 Maximal length of horizontal pipe and maximal sum of changes of direction when connecting toilets and other fittings.

Illus.3.7 Top connection.

collecting pipe. Top connection:

Must be avoided wherever possible. A top connection leads to serious disturbance in the horizontal pipe and hydraulic sealing may occur. Where there is no alternative then a top con- nection is permitted only where the horizontal pipe is at least 110 mm and the Q¡ of the connecting pipe is no more than 1 l/s. 45° and 90° redu- cing T-pieces may be used in this case (illustration 3.7).



Peripheral requirements for removal of waste water

Peripheral requirements for removal of waste water

3.4.1 Connections to stacks

3.4.2 Angled sections Angled sections must be avoided. It was previously believed that angled sections were useful in reducing the speed of fall. If an angled section is nevertheless unavoidable because of cables or other services, then the length of the branch may be 1.50 metre at most and the bends used may be a maximum of 45° (illustration 3.12).

3.3.3 Connection

separations and sequence (illustration 3.8)

- Method

Connections to the stack should be at right angles to prevent hydraulic sealing in the collecting pipes. With connections at less than 45°, pressure differences in the stack are lower but overpressure is created in the collecting pipe, which then requi- res additional ventilation. At high rates of discharge from the collecting pipe hydraulic sealing may occur in the stack immediately below the connec- tion. A 90° swept T-piece may be used to reduce the likelihood of this. The precondition is that the top side is straight, otherwise the solution is contra-productive. A variety of possible situations are shown in illustration 3.10. Where a toilet is directly connected to the stack, it is recommended that the upper surface of the water seal is at least 100 mm higher than the under- side of the pipe connecting to the stack. In the case of a connection to 110 mm that will mean that the upper surface of the water in the trap seal will be at least up to the upper surface of the connecting pipe. This prevents back-flowing foul water appearing in the pan. Mutual separations and angles of connection. In order to limit interac- tions the distance between pipes connecting to the stack must be greater than 0.5 m if the included angle is greater than 90° (illustration 3.11).

In order to prevent interactions as much as possible there are requirements set down for separation distances. The dis- tances are so selected that a subsequent connection smoothes out the flow from the previous connection, allowing ade- quate air to remain above the water level. The separation must be at least 5 x D of the collecting pipe. If the collecting pipe is at least 110 mm and the calculated Q¡ of the pipe furthest upstream is no more than 0.75 l/s then the distance may be 2 x D. If a toilet, dishwasher or washing machine is connected upstream of a floor-gully shower connection, then the separation must be at least 1 metre to prevent hydraulic sealing through the large quantities of water and siphoning of the shower trap seal. No other connection may be made for a length of 1 metre downstream of a toilet connection unless that other connecting pipe is provided with a discharge. Only toilets and no other fitting may be connected upstream of a toilet connection, unless the connecting pipe is provided with a discharge. The upstream fitting (not being a toilet) may be connected (at least 1 metre) downstream of the toilet connection (illustration 3.9). Strive to connect fittings with a high Q¡ to the upstream section of the col- lecting pipe, so as to prevent fouling and deposition as much as possible in that section. In order to prevent interactions as much as possible there are requirements set down for separation distances.

Illus. 3.9 Situation 6 from illustration 3.8.






1 any, unless a toilet

any, unless a toilet

5 x D

3.4.3 Stack foot and

any, unless a toilet

2 x D, if D 110 mm

2 any, if Q¡ 0,75 l/s

connection-free zones Overpressure is created by compression at the transition from the stack to a horizontal pipe or underground pipe. In order to prevent this, two 45° bends with an intermediate section of at least 0.25 metres should be used in place of a right-angle bend. This will smooth out the flow (illustration 3.13). Also noticeably less noise will be generated. Where a horizontal branch is required on a stack, connection-free zones should be established alongside both bends (illustration 3.13). 1 Metre connection-free zones are required for each 10 metres of stack length (between the horizontal pipe and the highest connection) where the stack joins a horizontal pipe. Where the stack length is between 10 and 20 metres the connection-free zones must be 2 metres long. Connection- free zones of 1 metre are required at the horizontal/vertical transition (illustration 3.13). The diameter required for the horizontal section is of course calculated as for common or underground piping, and the largest calculated diameter is used throughout. An alternative solution must be found where connections are nevertheless required in connection-free zones (illustration 3.14).

3 toilet, dishwasher or washing machine

floor gully shower

1 m (L1 )

4 toilet


5 x D

any, (no floor gully shower)

5 toilet

if with secondary discharge to B

5 x D

if connected

6 any (not a toilet)


1 m downstream of B, illustration 3.9

Illus. 3.8 Connection separations and sequences.

3.4 Stacks Since the upwardly extended section of the stack also serves as the vent line in a primary discharge system, great care must be taken to ensure that no hydraulic sealing or excessive pressure differences arise. A free flow of air, including the col- lecting pipework, is of crucial importance. The vulnerable areas are: the in-flow from the collecting pipework and any bends, including that at the foot of the stack where this enters the underground pipe, and any angled bends or horizontal branches in the stack. When waste water is discharged into the stack it will flow down, after passing a short length, more or less along the pipe walls. A column of air with some water will also be drawn downwards. The air and the pipe wall will slow the falling water. Depending on the diameter and the quantity of water, the

speed of flow will be between 7 and 11 m/s after 10 to 15 metres and will not increase beyond this. 5 to 12 times as much air as water is required. The supply of air via the ventilating pipe is therefore essential. It is important here that the stack is as straight as possible. An underpressure will be created in the upper section of the stack. This may not exceed 300 Pa for stacks used for remo- val of waste water (traps must be 500 Pa = 50 mm). The determination of diameter as shown in illustration 4.2 is based on this. The diameter of the stack may not be smaller than that of any one of the collecting pipes connected upstream. Overpressure will exist lower in the stack. In general no attempt is made to limit this, but its effect (the forced emptying of traps) is eliminated by establishing zones where no connections may be made.

Illus. 3.10 Various connections to a stack.



Peripheral requirements for removal of waste water

Peripheral requirements for removal of waste water

3.6 Ventilation pipes The ventilation pipe serves to admit and vent air to and from the discharge system. The diameter should be the same as that of the stack, ignoring any reduced section of stack. The diameter may be reduced by one step if all the following conditions are met: - total length of the stack is less than 20 metres; - length of the ventilation pipe is less than 10 metres; - total length of the ventilation pipe including the reduced stack section is less than 10 metres: - there are no more than 4 bends of 90°or 6 bends of 45°; - the reduction does not occur in the combined section of a ventilation pipe. Ventilation pipes may be horizontal. Ventilation pipes for several stacks may be combined into a single roof penetration provided: - the diameter is at least that of the largest stack; - the combined section is not reduced; - no more than 10 stacks are combined.

Particularly where there are several horizontal sections in the stack a balancing line must be provided (illustration 3.15). Each vertical section must be connected to the corresponding vertical section of the stack with a downward-facing 45° T-piece. The diameter of the balan- cing line must be at least 0.8 times the largest diameter in the relevant stack section. Connection-free zones are also applicable here. 3.4.4 Stack diameter This is calculated by taking the sum of the baseline discharges and the largest baseline discharge at the foot of the stack, using Illustration 4.2. Where the stack is connected with horizontal sec- tions as in illustration 2.5, 3.13 and 3.15, then the diameter must be established separately for each section. A reduction by one step in size is permissible for the upper part of the stack, provided the total length of the discharge pipe plus the reduced stack is no more than 10 metres. The diameter of the reduced stack section must of course remain at least as large as that of the connection above. 3.5 Underground pipes For underground pipes taking domestic waste water only, all the criteria apply as set down for stacks. Connecting pipes and stacks must be connected to underground pipes via a side connection, an oblique connection or a top connec- tion at 45° (illustrations 3.5, 3.6 and 3.7).

Illus. 3.13 Transition between stack /

Illus. 3.14 Connection in a connection-free zone.

Illus. 3.15 Example of a balancing line. See also illus. 2.4 and 2.5.

horizontal pipe and connection- free zones.

3.7 Roof penetrations The vent pipe is taken through the roof. A cap is usually fitted to the pipe end. Stench from the waste system may not cause nuisance. A number of require- ments and conditions are set down to achieve this: The outlet area for the outgoing flow must have at least the same surface area as the cross-sectional area of the discharge pipe. The vent pipe must protrude suffi- ciently above the roof (to take account of snow among other things). The vent pipe must not penetrate a wall. The vent pipe opening must be at least 1 metre above the highest point of any air opening (door, roof-light, ventilation opening). The vent pipe must be at least 8 metres from any: - roof terrace or other external space; - air opening (door, roof-light, ventilation opening) in the wall if the roof joins a rising wall.

facility should in any event be provided with an approval mark. Grey and also black water may be so purified that it can be used as a domestic water source. Contact the local authority for more information about the possibilities and obligations.

The foregoing will explain why ventilated roof tiles are strongly discouraged. In the case of buildings higher than 20 metres, or adjacent to buildings above that height it is possible that wind effects will create overpressure or underpressure around the vent opening. In that case the vent must be placed as far as possible from the roof perimeter or adjacent high wall.

Illus. 3.11 Separations and angles for connections to stacks.

3.8 Discharge of waste water

Grey or black waste water may not be discharged into the surface water or infiltrated into the ground without purification. In most cases the waste water will be led off via the local authority sewer. In certain circumstances in outlying areas where no sewer is available it may be permitted to purify the water to the extent that it can be discharged. Depending on the sensitivity of the area a simple or more advanced individual water treatment facility may be required. Such a



Illus. 3.12 Angled sections in a stack.

4. Dimensioning for waste water

5. Noise

gravity and a thick wall are therefore appropriate. Contact noise is a trouble- some phenomenon. All materials in contact with one another will vibrate together, little damping takes place and amplification may even occur. As the E-modulus of a material falls there is less spreading of noise. In order to reduce contact noise it is important that pipe walls do not make contact with one another or with other bodies. ASTOLAN®, the material used to make Wavin AS combines a number of positive characteristics in a unique way: it has a low specific gravity, a thick wall and a relatively low E-modulus. The expansion compensator ensures that a Wavin AS pipe has no direct contact with the next pipe. The pipes must be secured with brackets with rubber inserts so that minimal noise is transmitted to walls and floors. These walls and floors should preferably be of substantial mass so that it is difficult to bring them into vibration.

In general, it is considered good practice to keep the noise caused by discharge, as low as possible. In the Netherlands, requirements are set for noise reduction in NEN 1070 and NPR 5075. An optimal situation can be achieved by chosing a low noise pipe in combination with good installation practices. In living areas in an adjacent residence the level may not exceed 30 dB(A) while for edu- cational and working areas the figure is 35 dB(A). The Wavin range includes a special low-noise waste removal system designed to meet these requirements, Wavin AS. In this chapter we investigate the generation and transmission of noise in waste pipework and the measures that can be taken to limit noise nuisance.

Taking account of the minimum diameters stated in illustration 1.2 the required diameters can be read off for:

collecting pipes and underground pipes for removal of waste water (illustration 4.1); stacks for removal of waste water (illustration 4.2).

Noise from stacks

5.1 The generation of noise

1 = PVC without jacketing, pipework in test area. 2 = Wavin AS without jacketing, pipework in test area 3 = PVC with cellular concrete duct (56 kg/m 2 ) 4 = Wavin AS with cellular concrete duct (56 kg/m 2 )

Noise is generated in various ways in a pipe with flowing water: the sounds of flowing water and air, the noise of water impacting on water and of water impac- ting on the tube wall. Combating noise nuisance in waste pipework requires a combination of measures, the most important of which is: to prevent as far as possible that noise is generated. The design for a waste pipework installation must therefore ensure an optimal layout: little impact (so good pipe routing) with proper ventilation to ensure that the water can flow unhindered to counter bubbling and differences in flow rates. The pipe wall must be smooth to prevent irregularities in flow. 5.2 Noise transmission Noise will occur even with correctly routed pipework. Transmission of noise takes place in two ways: through the air (airborne noise) and through solid bodies in contact with one another (contact noise). A heavy intervening wall is required to limit the transmission of noise through the air. The lighter the pipe wall, the more easily the airborne noise escapes to the outside. High specific

A notorious source of noise is the transition from a vertical stack to

horizontal pipework. The Wavin AS range includes a variety of accessories to allow this transition to take place smoothly and few sharp changes in direction. Additionally this section is freely suspen- ded in rubber in the Wavin AS range and there are no brackets. Even with all these measures in place waste pipework may not pass through frequently occupied areas. Try to arrange routing so that pipework is kept as far as possible away from areas that must be kept low-noise. There must be at least one intervening wall between pipework and a frequently occupied room.

Illus.4.1 Capacity of horizontal HDPE pipework; 70% full, k = system wall roughness = 1 mm.

D 40 50 63 75 90 110 125 160 200 Qo in l/s 0,45 0,77 1,30 1,89 2,80 4,30 5,62 9,22 14,41

Illus. 4.2 Capacity of HDPE stacks with a maximum pressure difference of 300 Pa (30 mm of water).




6. Casting in heat cured concrete and extrusion shrinkage

Butt welding creates ridges on the interior and exterior of the pipe. The internal ridges can hinder the proper flow of foul water. An experienced welder will be able to make a sound welded joint with only minimal ridging. Electro-welded sleeves can be applied in critical situations. 7.1.2 Brackets Brackets must have sufficient strength to carry the weight of the complete pipe- work when full. Illustration 7.1 shows the suspension forces for filled HDPE pipework for various bracket separations. Brackets may have different functions: support, clamping or fixing. A support bracket serves to carry the weight of the pipe- work. If the pipework expands or shrinks it must be able to slide through the bracket (or the bracket must be able to follow the movement with little resistance, for example through the use of a long, slender suspension leg which will easily bend). Clamping brackets serve to fix the pipe with respect to the structure. The bracket must therefore hold the pipe securely and be attached to the structure limits are set down in the standards against set temperatures, and are for HDPE: at 110°C max. 3%. The pipe will expand during heating of the liquid concrete. The degree of expan- sion is limited as the pipework is fixed at various points and (the mass of) the concrete restricts expansion. Once the concrete has hardened the pipe will shrink due to thermal shrinkage and extrusion shrinkage. This is resisted by the hardened concrete as the pipework is held fast by bends, sleeves, T-pieces and similar, so that tensile forces arise in the pipe. The tensile forces give rise to con- centrations of stress which may lead to breakage. T-pieces are particularly susceptible to stress concentrations.

HDPE pipework gives excellent results when cast into concrete floors and walls (see Chapter 7, Installation). Concrete is sometimes brought to very high tempera- tures in order to allow shuttering to be struck the following day, particularly in tunnelling work. The temperature gauge controlling the burners may sometimes be defective. It is also sometimes the case that the control of the burners is carried out using the outermost tunnel sections, because these cool most rapid- ly. The temperature in the enclosed tunnel may then be appreciably higher. Extrusion shrinkage becomes significant for plastic

without excessive deflection. This method allows any changes in length to be transferred to places where these can be dealt with by means of bends, flexible pipe, expansion sleeves and so on. With HDPE pipework systems the pipes can be fixed so that no changes in length can occur. The forces generated can be taken up by the pipe- work itself and transferred to the structure via fixed point brackets. We then talk about "rigid installation" with fixed point brackets. Rigidly installed pipework has a tendency to undulate. This can be prevented with the use of rails or bearers (see 7.2.2). The degree of extrusion shrinkage depends on the maximum temperature achieved. It is clear that the temperature of the pipes may be no higher than 80 to 90°C to cut out all risk. Since the variation in temperature in the concrete can be fairly great, it is stipulated that the measured temperature shall be no higher than 50 to 60°C. Higher temperatures are in any case not good for the quality of the concrete. HDPE pipes for above-ground drainage are sometimes "tempered" for safety reasons. That means that they are heat treated during or following manufacture (extrusion), largely removing extrusion shrinkage.

5.3 Noise reducing measures 1. Waste pipework should not be located in the vicinity of occupied areas, and must never be led openly through occupied areas. 2. Good routing and ventilation cut down noise generation: Falling waste water should be led down smoothly in stages, abrupt descents are bad from a noise point of view. At the foot of the stack a calming section of 250 mm should be used at the transition from the stack to the horizontal pipework. The use of 2 bends of 45° with long legs is recommended here. Waste pipework should be dimensio- ned so that air can circulate freely along with the waste water. A gradually tapered reducer creates less noise than an inserted reducer does. Connections to collecting pipework or to underground pipes should prefera- bly be by means of side connections. Where top connection is unavoidable, then an angle should be employed. At the foot of the stack the axis of the horizontal pipe can be shifted around 1 x D with respect to the axis of the stack. This allows the water to cling better to the walls creating less noise. 3. A plastic pipe wall is and remains smooth so that flows are not disturbed. 4. The special ASTOLAN® pipe wall (Wavin AS) prevents airborne noise and contact noise. 5. The Wavin AS expansion compensa- tor prevents transmission of contact noise. 6. A rubber insert in the brackets prevents transmission to the wall, pipework must never make contact with walls or other materials.

5.4 Fittings Noise from fittings can be limited by:

7. Fixing to a heavy wall damps down contact noise (preferably > 220 kg/m 2 ). 8. No brackets should be located in impact zones. 9. A (heavy) intervening wall damps down transmission by air. 10. With dummy wall constructions the pipework should be secured to the bearing wall rather than to the dummy wall. 11. All wall and ceiling penetrations should be provided with rockwool or other elastic materials. This prevents direct contact between the pipework and the wall and the transmission of airborne noise from one room to another along the pipework. 12. Where a pipe duct is present, the inside of the duct wall must be provided with absorbent material (mineral wool). 13. With horizontal pipework below a false ceiling, provide extra insulation with lead foil at bends and connec- tions. Since the method of installation affects the generation of noise it is recommen- ded that the installation is carried out by well-trained fitters. Where the measures outlined above are implemented consistently, no additional noise insulation will generally be required.

anti-vibration insulation and anti-vibra- tion fixing of the toilet pan removal of reverberation by placing damping material below baths and shower trays reduce noise from water jets by using a small angle against the wall or by means of a perlator.

pipework in these circumstances. Extrusion shrinkage is the single-

occurrence shrinkage measurable when the pipe is heated and then cooled. The

7. Installation

The installation of waste pipework can be divided into the installation design and the installation itself with the actual work of fitting. The installation must be such that the pipework system can fulfil its function without problems and with the minimum of maintenance. The system must be able to handle changes in use, such as changes to the frequency of discharges or the temperature of the medium. The most important condition is that the system must be able to with- stand the loading generated in installation and use. These include: loading through the contents and the weight of the pipework itself; flotation forces when casting into concrete floors and in some cases with underground pipework; forces arising from changes in length due to fluctuations in temperature. This imposes a number of requirements on the design and installation of the system. 7.1 Design 7.1.1 Fixings Welded connections in HDPE may be either butt welds or electro-welded sleeves.



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