Modern Building Services

16 MODERN BUILDING SERVICES APRIL 2021 FEATURE PIPED SERVICES & PUMPWATER PIPED SERVICES A s all plumbers know, backflow is when stagnant or contaminated water gets sucked back into the mains water supply. There are two main causes, again well known – back- pressure or back-siphonage, which occurs when water is pushed in the opposite direction to its standard flow path. Back siphonage can occur if there is a sudden drop in pressure upstream of an outlet – for example from a burst pipe – causing the contents of the pipework to drain towards its source. In the event an outlet is open when back siphonage occurs – for example a garden hose being left to fill a pond – harmful contaminants could be pulled back into the potable water supply. There are many other appliances – for example baths, showers, washing machines, even swimming pools that are potentially a backflow or back siphonage risk. Ensuring the correct level of prevention or protection is in place is key. Battling backflow with regulations To help tackle the problem of backflow, the Water Supply (Water Fittings) Regulations (1999) for England and Wales (Byelaws in Scotland) have identified five fluid categories, each representing a higher degree of risk. Fluid Category 1 is considered safe, while Fluid Category 5 presents a very serious health hazard. These categories are important, and we’ll look at them in more detail shortly. The presence of contaminants in clean water presents a real and immediate risk to health. This is never good for any building, but it’s especially concerning in hotels, schools and hospitals and healthcare facilities. In these spaces, occupancy is high, the system is in constant use, and potentially vulnerable or at-risk users may be using the system. There’s also the potential for this backflow to enter themainswater supply, posing awider public health risk to neighbouring homes and communities. In extreme cases, building owners can face prosecution. Moreover, the process of draining and cleaningwater supplies results in significant disruption andwater waste, with all the sustainability implications that brings. As the regulations were introduced in 1999, backflow prevention is of particular importance to refurbishment projects and heritage buildings. Understanding the five fluid categories The key to navigating backflow regulations is understanding the expected level of fluid risk for the building in question, and what level of protection will be needed. Fluid category 1 and 2 Fluid category 1 – ‘wholesome water’ which complies with section 67 of the Water Industry Act 1991 – requires no specific countermeasures or action. Fluid category 2 covers water which has altered in either appearance or taste, with likely causes being either a temperature change or the presence of micro-organisms or other substances. Here, a single check valve will suffice. An example of this is a basinmixer tap, where hot water can sometimes pass back into the cold supply – installing a single check valve to the cold pipe feeding the tap would prevent cross flow fromoccurring. Fluid category 3 Fluid category 3 represents water with low levels of toxicity which nevertheless present a slight health hazard. In these cases, double check valves must be installed. One instance of this would be a supply to an outside tap – unless this supply is feeding a sprinkler system that uses pesticides, in which case higher protection is required. Backflow presents challenges and risk for commercial and public use buildings, but Reduced Pressure Zone (RPZ) valves provide an easy and reliable solution. Richard Bateman, Product Marketing Manager at RWC, looks at the legislation and the technology. Understanding backflow regulations and what they mean for you