10. Pressure testing
11. Maintenance
A well-designed, properly installed and correctly used waste removal system will require little or no maintenance. Inadequacies in design and installation, and above all incorrect discharge activities may cause poor or slow removal of water or a blockage. Usually no action is taken until the water begins to drain slowly or there is a complete blockage. Checks on drainage and periodic maintenance are therefore recommen- ded. In the event of blockages or threatened blockages which are not located in the traps, a clearing spring may be used. Care must be taken to prevent damage, especially in bends. High pressure cleaning with a jet head is a better approach. The use of explosive charges to cause pressure shocks in the pipes is not recommended. The usual drain-clearing agents may be used provided the instructions on flushing are followed. Roof channels, roofs, roof gullies and the like should be periodically cleared of dirt, leaves etc. Specialist firms may carry out major maintenance or the clearing of serious blockages. It is useful to build in a number of cleansing facilities to aid cleaning or removal of blockages: removable traps connections to underground pipes with rubber sleeves access fittings at strategic points such as at the transition from underground pipework to the domestic pipework, around hydraulic problem areas such as after a series of bends and with longer pipe runs, and in cast-in pipework. Access fittings must be accessible and where possible be located higher than the horizontal pipework, or better still higher than the discharge level of fittings.
This means that a section of the blocked pipework does not need to empty through the opened access fitting. Where the access fitting cap is more than around 100 to 150 mm from the exterior of the pipe, the use of a 45° fitting is recommended. Obstruction of drainage from roofs, gutters, gullies, overflows, rainwater drainage and other drainage constructions must be prevented by
Pressure testing is carried out most quickly and simply using air under a limited overpressure. This is also possible with internal rainwater systems. The simplest procedure is to close off all openings, apply air pressure of 2 to 3 kPa (0.2 to 0.3 metre water column) and apply soapy water to the joints. Specialised companies sometimes use smoke-testing. It is recommended that sections to be cast in concrete be pressure tested before pouring. This is not only because repairs are so difficult afterwards, but also to establish whom is to bear the cost of any subsequent repairs. If it is decided to carry out pressure testing (to NEN 3215) then the procedure is as follows: The system is pressure tested with an air pressure of 400 Pa (40 mm water column). Where the total capacity of the system to be tested is greater than 0.3 m3, then it must be tested in sections of 0.3 m3. All open joints are to be sealed with ball-type valves and all traps are to be filled. After 15 minutes the drop in pressure must not exceed 50 Pa (= 5 mm water column). If the drop in pressure exceeds that, the test must be continued up to 60 minutes. After that period the drop in pressure may not exceed 200 Pa (= 20 mm water column). The drop in pressure may be caused by moving connections, such as toilet sealing sleeves and sealing sleeves between horizontal pipes and connecting pipes, as well as by temperature differences during the test. The temperature difference may be up to 0.3°C, measured in the spaces occupied by the waste pipework.
The pipework must not be exposed to radiant heat, including the heat of the sun. Where this nevertheless occurs (usually prior to pouring of concrete) then pressurisation with air and soap testing of the joints is a good alternative. A test is carried out immediately prior to the pressure test in order to demonstrate that the equipment is in good order. For this purpose the internal pressure in an enclosed pipeline or hose of say ø10 mm and 2 metres in length, with the pressure meter attached, is brought up to 400 kPa. The pressure drop may not exceed 10 Pa (1 mm water column) in a period of 15 minutes. When that is the case the waste removal system may be placed under pressure and the actual test carried out.
means of periodic maintenance. Special attention must be paid to
drainage where granular roof coverings are installed after the drainage system is in place. Grit which enters horizontal pipework is difficult to flush away using the normal speed of flow, and encourages fouling. Flushing clean before handover and after around a year is strongly recommended.
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