WATER HYGIENE & SAFETY Causes of backflow
Backflow occurs when fluid flows in a direction contrary to the intended or normal direction of flow. This can happen by ‘back siphonage’ – where the water typically siphons from a higher to a lower level via pipes or fittings, or by ‘backpressure’ – where water is forced in the ‘wrong’ direction by a downstream pressure which is greater than that upstream. The water fittings regulations/ byelaws identify a number of backflow prevention arrangements and devices, each of which has been assigned a fluid category rating, which denotes the type and highest level of backflow protection it provides.
Point-of-use protection is located where the water is being discharged or used. This is the primary source of backflow protection for systems upstream of this point. It must provide protection against both the type of backflow and the highest level of fluid category risk, that the system, i.e. the fitting or appliance, could be exposed to. Point-of-use protection can take many forms – from mechanical devices to physical tap and air gaps; in the case of appliances, it is often, but not always, built in.
Zone and whole site backflow protection
Zone protection (Fig. 1) may be required by a water company to protect against backflow between different parts of the same premises. As a guide, the level of backflow prevention will be one fluid category lower than the highest level of risk identified in the zone to be protected. Whole site backflow prevention (Fig. 2) is installed to safeguard the public water supplies, but does not relax the
Water
undertaker’s main
Site boundary
Whole site protection
Individual applications, each with their own backflow prevention as required
Figure 2: Whole site backflow protection.
requirement for other required backflow prevention provision. The level type and position of whole site backflow prevention, if required, will be determined by the water company.
Communication
While in some areas water companies have been involved in the process from the start, sadly this has not been the case for all. In far too many instances the first that water fittings teams learn about a COVID-19 site is through media coverage. Just because there is an existing water supply on site does not mean that the water companies should not be consulted on proposed alterations to plumbing systems. Given that we are in the midst of the greatest national emergency we are likely to face in our lifetimes, water
companies are unanimous; they do not want to slow down the construction of any essential sites, but need to be involved, and in communication with those responsible on site. It is important to remember that water companies have a legal responsibility to safeguard public water supplies,4
and water fittings teams
need to make sure the plumbing on site is fully compliant with the water fittings regulations/byelaws. They too should be involved in local resilience forums.
Lack of access
In addition to the lack of communication, some water fittings teams have been told they cannot access sites. This response is disappointing given that water companies are going to great lengths to work with those responsible for these sites – offering
June 2020 Health Estate Journal 37
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