What the backflow regulations mean for you

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Backflow presents challenges and risk for commercial and public use buildings, Richard Bateman, Product Marketing Manager at RWC, looks at the legislation and how to safeguard against backflow.


As all plumbers know, backflow is when stagnant or contaminated water gets sucked back into the mains water supply from back-pressure or back-siphonage.


Back pressure occurs when water is pushed in the opposite direction to its standard flow path while back siphonage can occur if there is a sudden drop in pressure upstream of an outlet causing the contents of the pipework to drain towards its source. Ensuring the correct level of prevention or protection against backflow is in place is key.


Consider the backflow regulations


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.


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.


single valve

An example of this is a basin mixer 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 from occurring.


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.


double check valve

The valve you choose must be compliant with the Water Supply Regulations 1999. Part of RWC’s family of brands, the JG Speedfit range of plastic push-fit fittings offers a Double Check Valve with a Stop Valve. The stop valve isolates the water supply to the outlet, for installers to easily service the outlet that the valve is connected to instead of needing to shut off the whole building’s water supply.


Fluid category 4


The more significant health hazards begin with Fluid category 4, which is water with harmful concentrations of toxic substances. Suitable backflow prevention devices are required in these situations, such as RPZ valves. Reliance Valves’ Reduced Pressure Zone (RPZ) Valve, for example, is one of the safest and most reliable backflow preventers available for commercial (fluid category 4 risk) applications.












This device is a verifiable assembly, that is designed to be regularly tested, to ensure the higher risk of potential contamination is limited. In the event of a drop in pressure or back siphonage occurring, the mains water supply is protected by diverting the back-fed water from a property out to a waste pipe, therefore diverting it from the main supply and drinking network, limiting the risk of contamination. Applications include commercial dishwashers and cleaning appliances, commercial heating systems and fire sprinkler systems where anti-freeze is not used.


Fluid category 5


The highest risk level of all – Fluid category 5 – represents the most serious health hazard because of the presence of pathogens and radioactive or very toxic substances. Fluid category 5 is a highly specialist area calling for a Class 5 backflow prevention device, incorporating a Type AB air gap or equivalent.


Clearly, backflow presents significant risk. However, there are easy and efficient ways to prevent it from happening, and to ensure an uninterrupted supply of safe clean water. These solutions are available from RWC’s Reliance Valves range, together with the support of an experienced technical team that’s able to offer installation advice and best practice guidance. With backflow, we really do have your back.


For more about RWC and Reliance Valves, please visit www.rwc.co.uk.



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