Figure 1: Risk assessment for Legionella via review of the domestic water installation.
unclearly documented; e.g., it has not been clarified how temperature and flow conditions play a role together.
The new EU drinking water directive will increase the focus on Legionella as well as direct or indirect on the risk assessment of domestic water installations.
Nationally and internationally, there is relatively limited regulatory encouragement to search for alternatives to temperature protection against Legionella.
Due to the dilemma between protection against Legionella in domestic hot water and achieving high energy efficiency
Part of installation
Parameter influencing Legionella-associated risk
Severity for Legionella risk
Likelihood for occurrence in actual period (e.g. a year)
Controle procedure avoiding occurrence or mitigating risk
Risk-score contribution
R I S K
S E V
O C C
D E T
Unit/ Component
Parameter
Value
Potential impact
Possible cause
Detection controle
Which parameter tobe investigated? Select from list
Which value assumes the parameter, compared to what is allowed to?
Potential effect in words and numbers?
Possible cause in words? Select from list/ Own assessment
Procedure for detection and control?
Risk-score contribution
Select from list/ Own assessment
Select from list / Own assessment
Select from list/ Own assessment
Legionella.spp; Measurements performed & Legionella detected
Moderate content of Legionella.spp.
From pumped drinking water
Cold-water supply
Legionella
5
100%
Non
0%
31
Temperature
0 - 20 °C; Temperature OK No growth of Legionella
0
100%
0%
0
Cold-water supply
Temperature
0 - 20 °C; Temperature OK No growth of Legionella
0
90%
0%
0
In periods 20 - 25 °C; temperature too high
Moderate risk of Legionella growth
Temperature
5
Poor insulation
10%
Non
0%
3
24 pcs. rarely-used tapping points at waste chutes
Dead ends or rarely-used pipes
Rarely-used cold-water pipe
Moderate risk of Legionella growth
6
50%
Non
0%
31
Temperature prevents growth of Legionella Considerable risk of Legionella growth
Hot water supply
Temperature
> 50 °C; Temperature OK
0
100%
0%
0
Often 45 - 50 °C; temperature low
Inappropriate type thermostatic valve
Temperature
6
100% Non (will be replaced)
0%
62
Water replacement often less than 1 times per day
Small risk of Legionella growth
Water flow
3
Insufficient pump capacity 100%
Non
0%
7
Figure 2: The risk assessment tool illustrating initial risk factor screening
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