WATER SAFETY PROCEDURES
60˚C Pump
60˚C
Calorifiers continuously pasteurise the water in the hot water circuit
20-45˚C Pump
20-45˚C
Under heavy demand calorifiers
cannot heat water sufficiently and pasteurisation does not occur
TMV
TMV
43˚C from tap
Demand rate from tanks does not exceed
mains input rate to tanks, so
tanks remain full Pump set
Path of least resistance
(temp. = 10˚C)
Stagnant cold water tank (temp. = 17˚C)
Legionella from tap
Parallel cold water tanks are difficult to balance
Demand from tanks exceeds mains input to tanks, so levels in both tanks drop, drawing stagnant water into service
Pump set
Stagnant cold water
Figure 1. Potential Scenario – Normal Demand.
tap for two minutes (standard practice) means that the water temperature being tested is approximately 50 metres from the outlet (because this is the amount of pipe ‘emptied’ by running a tap for two minutes, see Table 1).
Para. 7.30, ‘Drinking water’, suggests that separate drinking water systems are likely to have infrequently used outlets (because the volume of water necessary for drinking is small compared to the pipework volume). It would be possible for an Estates team to determine whether dedicated drinking water systems are present in a particular property. One might also expect a risk assessor to have recognised this and recommended elimination (but this almost never happens).
Appendix D.22, which relates to Pseudomonas aeruginosa, states: ‘Risk- assess the water system for redundant pipework and dead-legs (for example, where water is supplied to both the cold water outlet and a thermostatic mixing valve (TMV) supplying an adjacent blended water outlet, as such cold water outlets in augmented care units may be infrequently used)’. This is consistent with the statement I commonly make, that patients typically only use cold water to drink or clean their teeth. The drinking water tends to come from a jug. The washhand basin cold water is then only for teeth cleaning, which is likely to be done only at a few of the washhandbasins present. Clinical washhandbasins (i.e.
Figure 2. Potential Scenario – High Demand, e.g. during flushing.
those for staff) would probably never need separate cold water supplies. If drawings/schematics can be relied upon, then in principle an Estates team could predict these infrequently used outlets.
Impact of single-bedded rooms HTM.04 Part C,6
para. 2.1, acknowledges
that the provision of single-bed rooms with en-suites, and the promotion of hand hygiene, have increased the number of infrequently used outlets and low water throughput. It therefore makes sense to start any search for infrequently used outlets in wards which have single bedrooms with en-suites. The HTM guidance does not state who is responsible for identifying infrequently used outlets. Generally, health and safety law and guidance are based on the premise of ‘control and influence’. The water outlets in a ward/unit exist because the healthcare providers wish them to be present. The occupier has absolute control over whether or not those outlets are operated, and can identify those which are infrequently used. An Estates team can only effectively identify infrequently used outlets in the areas they directly control – plant rooms, their offices, workshops, etc. However, the Estates team has ‘influence’ in the sense that it may, during its routine activities, notice outlets which it suspects are infrequently used. It is bound by a duty of care to report these to the head of the ward/unit, for confirmation of their status, with a view to elimination or flushing.
Frequency of flushing
There is no difference between taps and showers. The previous guidance (HTM 04: 2006, Part B)7
How often should a shower or tap be flushed while in normal use and infrequent use conditions? The current frequency of flushing cited in guidance documents (which is the same for both showers and taps) is ‘weekly or as indicated by the risk assessment’,5 care units.6
and ‘daily’ for augmented recommended
twice-weekly flushing. Prior to that HTM 2040: 19938
only referred to flushing prior
to occupation and temporary closure of wards and departments, stating a duration of three minutes, and a frequency of weekly. There is a school of thought that says infrequently used outlets should be flushed until the temperature of the water is within critical control limits, which for hot water would mean 55˚C from the outlet (or inlet to a TMV). I have known people to flush outlets for as long as 10 minutes to achieve this temperature, which, as one can see from Table 1, could be the equivalent of emptying 200 metres of pipe. If it is taking that long to achieve a temperature, there is clearly something very wrong, and the flushing and ‘tick boxing’ are only hiding it. Particularly for hot water systems, it is important to study BMS plots of hot water calorifier temperature to verify that flushing exercises are not flattening the calorifier. Figures 1 and 2 illustrate the potential consequences of over-flushing a system. There is no particular benefit to flushing
November 2020 Health Estate Journal 57
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