Adequately protecting water supplies from backflow is crucial for the undisrupted operations of commercial and public use buildings. In this blog, we discuss how Reduced Pressure Zone (RPZ) valves can prevent backflow in commercial and public buildings. We’ll also explain where this hazard can happen, the dangers it can pose, what to consider when selecting an RPZ and what your responsibilities as a plumber are.
Backflow is when wastewater flows back into the pipes that deliver fresh water to your building (it’s also known as back-siphonage).
There are two main causes for backflow:
1. A sudden drop in pressure
In most modern plumbing installations, the mains water supply is maintained at a high pressure which is needed for showers and other water outlets. A sudden drop in this pressure can cause a vacuum effect, which can lead to stagnant water flowing back into the system.
2. Back pressure
Back pressure happens when a system is operating under higher pressure than the water mains, causing a reversal in the flow of water. An example of this is when increased pressure builds up in an unvented hot water cylinder, due to thermal expansion. Without adequate protection this could result in a ‘crossflow effect’ pushing the water down the cold supply feeding it.
The dangers of backflow
In a commercial setting, like offices, schools, hospitals and hotels, backflow can have a widespread impact. For example, chemicals found in wastewater could be toxic or the growth of microorganisms could cause serious illnesses.
One case documented by the Water Regulations Advisory Scheme (WRAS) shows just how dangerous it can be. A primary school in the south of England found that water coming out of drinking fountains was above 57⁰C in temperature. This happened because water from the heating system was backflowing into the cold water system.
Reducing the risk of backflow in public use buildings
There are a number of devices installers can use to prevent backflow depending on the WRAS Fluid Category the building falls under.
There are typically five fluid categories defined by WRAS, with Fluid Category 1 posing the least and category 5 posing the maximum risk. Most commercial and public use applications are likely to be deemed a Fluid Category 4 risk. This is due to highly concentrated toxic substances that are regularly used in these premises, such as harsh cleaning products.
Any building that presents a Fluid Category 4 risk, must install a Reduced Pressure Zone (RPZ) Valve at every point that connects to the mains water supply. These valves are intended to prevent contaminants from entering the water mains and should be installed, commissioned, tested and maintained by WRAS approved RPZ installers, who can be found on the WRAS website.
Choosing the right RPZ Valves
The two main things to consider when selecting an RPZ valve for your installation are: ease of installation and maintenance. This is because disruption to the water supply in commercial buildings such as offices, hotels, hospitals and schools can have a major impact on their operations.
This is where having a safe and reliable backflow prevention device, such as Reliance Valves’ Reduced Pressure Zone (RPZ) Valve, is vital. This product is a verifiable check valve assembly, designed to be regularly tested to prevent the risk of potential contamination. In the event of a pressure drop or back siphonage, the back-fed water is diverted away from the main supply and drinking network and out to a waste pipe.
Once this valve has been installed, it must be tested, and the installer must notify the water authorities regarding the status of works that have been carried out. As outlined in the “Water Undertakers’ Approved Installation Method” (AIM) Document, published on the WRAS website, it is essential the valve is tested every year to ensure that it is in good working order.
The RPZ Valves from Reliance Valves are easy to maintain and service too. They come with dedicated test points as well as upstream and downstream water isolation to enable faster repair and maintenance works.
For retrofit projects, choose Reliance Valves’ Compact RPZ Valves
Whenever you are working on a commercial building, it is crucial to check that the water system is adequately protected against backflow. Particularly for properties built prior to 1999, it is even more important to check for RPZ Valves, as they were built before the UK Water Supply Regulations (Water Fittings) or Scottish Byelaws were implemented.
But installing RPZ valves in older buildings comes with its own set of challenges, as they weren’t accounted for when the building was constructed. Meaning, you might have to work with limited space. For these projects especially, we have designed Reliance Valves’ Compact RPZ Valve. Available with ½” and ¾” size pipe connections, this valve can be installed in a confined area and could be fitted in either vertical or horizontal orientations to suit the application.
Protecting water supplies from contamination
As a plumbing engineer, it is important to know where backflow can happen and make sure that adequate preventive measures are put in place. By protecting our water supplies, we can ensure the smooth functioning of our commercial and public-use buildings.
At RWC, we’re with you all the way, from technical support to help you source a complete range of reliable and quality approved backflow prevention devices to suit any application.