What constitutes a non-compliant installation?

What constitutes a non-compliant installation?

Examples of non-compliance are below!

(Unvented Water Heaters)

What is non-compliant?

What is constitutes a non-compliant installation?


Did you realise that hard piping the pressure relief valve to the waste pipe (like the one in the picture) is non-compliant and does not conform to the Regulations?

Do you know WHY this particular installation contravenes the Regulations?

1/ It is hard piped to drain

Why is this important? The incoming mains cold water to the water heater is in direct fluid communication with the category 5 foul water drain. If the drain ever blocks contaminated water, bacteria and pathogens can backflow/backsiphon into the potable/wholesome water and contaminate the cold water supply.


To rectify this, an air break to drain must be fitted. Due to the category of the could drain (category 5 hazard) a single or double check valve (on the cold water feed) is not deemed to be suitable protection. A suitable device to provide a solution would normally be a standard tundish. The standard tundish provides two solutions in one, it becomes a visible means of discharge and has the backflow and back siphonage protection. However, if the “D2” is connected to waste then a further problem is introduced which then needs a solution.

A standard tundish has no way of stopping foul odours or gasses from entering back into the building, a wet trap cannot be used as it would dry out. Therefore a dry trap (such as a hotun) has to be used.

2/ It has no visible signs of discharge

Why is that important? Without being able to see if water is dripping from the PRV, a building user will not know there is something wrong with the system and the water will continuously be wasted without any remedial repair being undertaken. In terms of Water Regulations, this will be deemed as undue consumption and a misuse of water.


Fitting a tundish provides the visibility required 


Consequences for the homeowner or building user

If an installation is non-compliant a building owner/user, upon investigation, would normally be issued with a non-compliance notification. If the building owner/user fails to rectify the notice they would then be served with an enforcement order/notice, if they still fail to comply they could be criminally prosecuted and if found guilty, receive a conviction and a fine.

We see many, many water heater pressure relief valve discharges installed like this one, in fact the problem is so widespread that Severn Trent and Yorkshire Water have stated that well over 50% of installations are installed non-compliantly! 


But if so many are fitted this way non compliantly Why are they fitted this way?

Is it because the installer;

1/ Had no knowledge of the requirements?

2/ Had a lack of cost-effective credible alternatives?

3/ Was unaware of the current water and building regulations?

4/ Had simply always done it that way and no one had said anything was wrong?


Now there is no excuse for a non-compliant installations!

Typical Small Water Heater Installation

hotun has been invented so that installations can pipe their unvented hot water PRV discharge to a local drain compliantly – quickly and easily.

How to make the installation compliant


How to make the installation compliant


hotun allows the installer to pipe the discharge from the PRV, locally to a foul waste or soil pipe.

What the hotun solution provides

In order to make this example compliant, we need to look at what the installer needs to achieve

  1. Provide a visible means of discharge
  2. Allow the PRV water to be safely conveyed to a point of discharge
  3. To ensure that the category 5 risk contamination water (in the foul drain) cannot back siphon or back flow into the wholesome water supply
  4. Ensure that no foul odours can escape back into the building from the foul drains

This is what the hotun dry trap tundish has been specifically designed to achieve – an all in one product solution

Fitting a standard tundish provides the first three protections but, up until hotun was designed and marketed, the installer would have had to have fitted a separate type of dry trap to stop the foul odours. This takes time and adds extra expense

Therefore if you cant discharge pipe to a safe point of discharge outside or it’s not cost-effective to do so, fitting hotun is cost-effective, quick and easy;

Why fit a hotun dry trap tundish?

Be fully compliant, easier, quicker and less costly!


Now there is no excuse to be non-compliant


No other dry trap solution provides compliancy at the point of

installation and visibility at the point of diagnosis!

Note – High volume T/PRV discharge pipes (as opposed to PRV discharge) should NEVER be connected to a waste pipe if that waste pipe is connected to a sanitary appliance. The high-temperature full flow discharge could back up into the sanitary appliance (a basin for example) overwhelm the appliance capacity and spill uncontrollably onto the floor. This is a very dangerous situation and must be avoided.

Discharges from appliances with Pressure Relief Valves (not combined T/PRV’s), are not a high volume flow risk

Due to the nature of operation of a PRV, it is RA Tech’s opinion that a connection from a PRV could be connected safely to a local waste pipe.

Severn Trent Water and Yorkshire Water estimate that at least 50% of all under-counter unvented water heaters are installed non-compliantly!

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