Three key plumbing regulations you need to be aware of

Wooden gavel with open law book and splashing water on table.

There are several heating and plumbing regulations that installers need to be aware of to make sure they’re protecting public health, promoting efficient use of water and safeguarding homeowners from costly repair work that could be avoided.

These regulations set out requirements for the design, installation, operation and maintenance of plumbing systems, water fittings and water-using appliances. As an installer you need to make sure you’re following the right protocols. Otherwise, you are risking the likelihood of hefty fines and even, in some cases, prosecution.

Here are three key plumbing regulations you need to be aware of, covering topics on preventing backflow, standards in best practice pipework installation and guidelines around the use of thermostatic mixing valves (TMVs).

1. The Water Supply (Water Fittings) Regulations (1999) for England and Wales (Byelaws in Scotland):

Established in 1999, this plumbing regulation defines the five fluid categories and the type of backflow prevention device required, to mitigate the risk of contamination. Fluid category 5 is the highest potential risk to health, and fluid category 1 being the lowest.

What is backflow?

Backflow happens when tainted or stagnant water is drawn back into the mains water supply, often caused by back-pressure or back-siphonage. This is when the water is pushed in the opposite direction of its normal flow pattern.

It is often caused by a sudden large drop in mains pressure within a property, for example if a pipe burst in the road. As the water drains to the damaged section, the water within the property rushes towards the fracture, creating a vacuum effect at any water open outlets. If an appliance is being used at this time, such as a washing machine with no adequate backflow prevention device on its supply, the risk of contamination to the potable water supplied by the water authority is high. This is often referred to as back-siphonage.

Another contamination risk is the potential for hot water to pass back down the cold supply, often referred to as cross flow. This can be caused by an imbalance in pressure between hot or cold supplies at a tap and could potentially lead to bacterial contamination. Another potential cause is thermal expansion and an example of this is in the case of an instantaneous hot water heater. As the hot water heats, it expands and if no adequate backflow prevention is in place, this can cause the hot water to pass back down the cold supply to the unit.

Preventing backflow is key to keeping our water supplies sanitary and safe as it can lead to health problems if someone consumes contaminated water. This is why the Water Supply (Water Fittings) Regulations (1999) for England and Wales (Byelaws in Scotland) established the five fluid categories, which are:

  • Fluid Category 1 – known as ‘wholesome water’ meaning it complies with section 67 of the Water Industry Act 1991 and doesn’t need to be addressed with any countermeasures or actions.
  • Fluid Category 2 – refers to water that has altered slightly in either appearance or taste, which could have been caused by a temperature change, the presence of micro-organisms or other substances. This will need to be addressed with a single check valve.
  • Fluid Category 3 – the category where water begins to become a health hazard as it’s water that has low levels of toxicity, which presents a slight health hazard. To tackle this problem, a double check valve will need to be installed.
  • Fluid Category 4 – water has harmful concentrations of toxic substances which present a significant health hazard. This calls for suitable backflow prevention devices, such as RPZ valves.
  • Fluid Category 5 – the category that presents the most serious health hazard because of the presences of pathogens and radioactive or very toxic substances, this requires a specialist prevention device.
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2. Water Regulations Schedule (WRS) 2.7

The Water Regulations Schedule was created to help installers (and therefore protect homeowners) by ensuring best practice when installing pipes to avoid the consequences of any substandard installation. This plumbing regulation covers where and how pipes should be run into buildings with a mains water supply – but not underfloor heating or manifold systems for radiators.

WRS 2.7 ensures that there are no inaccessible fittings concealed within flooring; this is to prevent homeowners from facing the costs of a pipe leaking within the floor. It also states that the entire length of a pipe has to be covered within a conduit, which is a protective sleeve for the pipe, so that it is easily removable.

To find out what pipes, fittings and conduits you can use to ensure you comply with the Water Regulations Schedule 2.7, read our blog here.

3. Thermostatic Mixing Valve Regulations

There are two main plumbing regulations for thermostatic mixing valves (TMVs), the TMV2 and TMV3 schemes.

Governed by Part G of the building regulations the requirement for TMVs states that hot water at a bath mustn’t exceed 48°C. This applies to all new build properties as of 2010.

Within commercial applications, the risk of scalding is potentially higher, due to the higher volume of system users. Therefore, it is recommended for installers to adhere to guidance set out by the relevant TMV scheme.

TMV2 is the standard for installation, commissioning, and maintenance of TMVs within a domestic (landlord) or commercial applications like service stations, leisure centres, and schools.

TMV3 sets out the standard and requirements for installing, maintaining and testing TMVs within a healthcare setting. Its requirements are slightly higher than the TMV2 scheme as the system user is at a higher risk and could be deemed vulnerable. Although both schemes are non-compulsory, they are an essential way to help limit the risk of scalding, while allowing high water temperatures to reduce the risk of bacterial waterborne diseases from spreading within the hot water system - legionella being the most common in most cases.

There are different heating and plumbing regulations you need to meet depending on your project. For example, a group of basins, public toilets or showers in a gym can be served by a single TMV, however, as mentioned, the requirements are different in a healthcare setting. Our Reliance Valves’ Easifit TMVs can help you comply with the regulations, while being simple to install in almost all spaces. Find out more about how to install them here.

Need advice?

For support with products or installation advice that can help you conform to these regulations, get in touch with our experts today.

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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.