Say no to backflow – Backflow prevention tips

Prevention tips for taps with backflow

Backflow prevention is crucial in both residential and commercial buildings, as it ensures the safety and hygiene of water. When water is contaminated, it can cause several problems, from diseases to plumbing issues. In our latest blog, we talk about how backflow can be prevented to keep our water supplies safe and clean.

What is backflow?

Before we go any further, you might be thinking what is backflow? Under normal circumstances the mains water supply in a building flows in one direction to feed outlets like taps or showers. However, when there is a big, instantaneous drop in pressure or a break in the main water line, there’s a high risk of dirty water flowing, or siphoning, backwards into the main water supply due to reduced mains water pressure. This is known as backflow or back siphonage.

Why does backflow happen

Why does backflow happen?

Backflow often occurs when the pressure in the mains water line significantly drops. In most modern plumbing installations, the mains water supply is maintained at a considerably high pressure to ensure desired flow from outlets. In the event this pressure ‘drops’ – for example if a water main in the road bursts/ or a distribution pump cuts out – the water will rush back down to the source or break in the pipe, causing a vacuum effect. Outlets served by this mains supply will suffer a backflow effect, possibly allowing dangerous contaminants into the water supply. An example of a high-risk area could be a shower head left in potentially stagnant bath water. This could be dangerous if backflow takes place and could contaminate the entire water supply.

Stagnant water can contain all sorts of harmful bacteria, chemicals and microorganisms. Below are some examples of what this dirty water can contain:

  • Fertilisers and/or pesticides
  • Human or animal waste
  • Chlorine from public swimming pools and spas
  • Soaps and detergents from bath, sinks, dishwashers and showers
How can you prevent backflow

How can you prevent backflow?

Backflow can be prevented through backflow prevention valves, such as a double check valve or single check valve. These valves allow water to flow only in one direction and prevent backflow and contamination of water supplies from external sources, such as wastewater in washing machines and dishwashers, or hosepipes that are submerged in garden ponds.

Choosing the right backflow prevention valve

When it comes to choosing the right backflow prevention device, it will depend on the fluid category the installation fits into. These fluid categories are defined as follows by the Water Regulations Advisory Scheme (WRAS):

  • Fluid category 1 – wholesome water complying with the requirements made under section 67 of the Water Industry Act 1991. There is no action required here.
  • Fluid category 2 – water in fluid category 1 whose aesthetic quality is impaired by a change in temperature and/or the presence of substances/organisms causing a change in taste, odour or appearance. The use of single check valves is required here.
  • Fluid category 3  –  fluid which represents a slight health hazard because of the concentration of substances of low toxicity. The use of double check valves is required here.
  • Fluid category 4 – fluid which represents a significant health hazard because of the concentration of toxic substances. The use of Reduced Pressure Zone (RPZ) valves is required here, and the commissioning and testing of these valves must only be carried out by an accredited tester approved by the local water supplier.
  • Fluid category 5 – fluid which represents a serious health hazard because of the concentration of pathogenic organisms, radioactive or very toxic substances. These situations require a Class 5 backflow prevention device which will incorporate a Type AB air gap or equivalent.

 working in domestic properties will need to handle fluid categories one to three and plumbers working in commercial buildings will experience all five categories.

Double Check Service Valve

Double Check Valves are Best for Domestic Plumbing

In domestic plumbing applications, the best practice is to install a double check valve with outlets where chances of backflow are higher to keep the water supply safe and clean. This type of valve features two internal valves to provide additional safety. If one valve fails, the other valve can still prevent backflow and contamination of the mains water supply.

The UK’s Water Regulations state that a double check valve should be fitted near the tap and after any other appliances or tees and the valve you choose must be compliant with the Water Supply Regulations 1999.

Under RWC’s family of brands, there are a whole host of double check valves, each with unique benefits. For example, the JG Speedfit range of plastic push-fit fittings offers a Double Check Valve with a Stop Valve. The handy stop valve isolates the water supply to the outlet, so you can easily service the outlet that the valve is connected to instead of needing to shut off the whole building’s water supply.

For plumbers who are working in smaller, more confined buildings, alternative options such as the SharkBite® Double Check Valve featuring our brass push-f­­­it technology for areas where a metal system is preferred, allowing for a fast, secure and solder-free connection.

Some white appliances such as washing machines and dishwashers may require single check valves that comply with the WRAS regulation. Valves such as our  Floguard® Single Check Valves are manufactured from DZR brass and are WRAS approved in accordance with the Water Supply (water fitting) Regulations 1999.

Reliance Valves’ Reduced Pressure Zone (RPZ) valve

Use Reduced Pressure Zone Valves in Commercial Applications

For commercial environments such as restaurant kitchens or hotels, it is vital that the appropriate commercial backflow prevention devices are used. If inappropriate backflow prevention devices are selected, or the requirement is ignored, the risk of health hazards increase. This can even lead to commercial properties being immediately shut down while the system is drained, and a safe supply of water is guaranteed. In turn, the installers’ reputation is at risk, and they may even be liable for damages.

For the ultimate peace of mind, Reliance Valves’ Reduced Pressure Zone (RPZ) valve is one of the safest and most reliable backflow preventers available for commercial (fluid category 4 risk) applications. This device is a verifiable check valve 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.

Say no to backflow

Say no to backflow

It’s critical to know where and how backflow could occur and put in adequate measures to prevent it from happening. On a small domestic scale, it can affect an individual home’s water supply, and lead to dangerous situations where end users can potentially consume contaminated water.

On a large commercial scale, a contaminated water supply can lead to a building or an entire community of buildings’ water supply being compromised. This means the business needs to shut down until the storage reservoirs are cleaned, resulting in the loss of hundreds of gallons of water and peoples’ lives being disrupted.

With a complete range of reliable, quality-approved backflow prevention devices to suit any application, plumbers can easily prevent backflow and the associated issues of backflow from happening.

Discover our range

Reliance Valves Backflow Prevention Valves keep water supplies sanitary and safe by protecting plumbing systems from contamination, back pressure or back siphonage. 

Richard Bateman Headshot

Richard Bateman

Product Marketing Manager Plumbing and Heating

About the author

A highly experienced and passionate professional, I have over 15 years' experience as a commercial and domestic plumber and hold NVQ Level 3 qualifications from City and Guilds

Since joining RWC in 2015, I began as a technical engineer, utilising my extensive knowledge to provide exceptional support. Currently, I am thrilled to be working with the marketing department as a Product Marketing Manager. 

This role allows me to combine my technical background with a keen eye for market trends, ensuring that RWC's products meet the evolving needs of the industry. With my wealth of experience and commitment to excellence, I am proud to serve as a spokesperson for RWC, sharing our innovative solutions and contributing to the growth of the plumbing and heating sector.