Two years ago, I was asked by a local company to remove an existing coffee machine and replace it with a wash up area. There was already a cold water supply to the location.
The only option we had for waste was to fit a macerator, as the location in question was in the middle of the building.
We decided to fit a small unvented water heater (15l) with a safety pack (inlet pressure reducing valve, NRV, expansion vessel and PRV). I knew (and the instructions confirmed) that I should fit a tundish after the PRV. What the instructions didn’t tell me was how to stop smells coming back out of the macerator if I connected the discharge from the tundish to it.
Anyone who knows about the Water Supply (Water Fittings) Regulations 1999 will know that they are legally enforceable and it is the water suppliers that are responsible for their enforcement.
The regulations, have three primary areas of concern.
1. Preventing contamination of wholesome water
2. Preventing the waste and undue consumption and misuse of any water
3. To make sure that the water fitting(s) used and installed are safe and do not cause or lead to erroneous measurement.
Specifically related to unvented cylinders when we connect the PRV discharge direct to internal drain, there are several, inter-relating Water and Building regulations that need to be met:
1. You should use a device as visible means of discharge and have an air break to drain facility. If a standard tundish is used, the tundish must be manufactured in accordance with the WRAS test code sheet number 221210 (date of issue No2 July 2000) “for all fittings incorporating a connection to drain facility.” (Derived from prEN 1717. Section 9).
2. Water Regulations section 6.3 – Regulator’s specification for backflow prevention arrangements and devices for the requirement for fittings – and section 6.4 Guidance clauses related to schedule 1 : Fluid categories; and Paragraph 15 of Schedule 2: Backflow prevention – Come into effect as we are directly connecting the wholesome water supply with a fluid category 5 hazard. Therefore any such connection must have an “air break to drain facility” (see 1. above)
3. Water Regulations Section 8 Schedule 2 G19 Discharge pipes from safety devices; G19.1; G19.3; & G19.4.
4. Building Regulations G3 (2) “….[pipework installation is] constructed and installed so as to resist the effects of temperature expected….”
5. Building Regulations G3 (3)(b), “ensure that any discharge from safety devices is safely conveyed to where it is visible……….”
6. Building Regulations G3 Guidance notes 3.50 discharge to tundish; 3.54 tundish requirements and Note; 3.55 visible means of discharge; 3.58 tundish outlet size; 3.60 a. a connection to a soil discharge stack and must “contain a mechanical seal not incorporating a water trap, which allows water into the branch pipe without allowing foul air from the drain to be ventilated through the tundish”.
7. Building regulations H1 Guidance: c. “….prevents foul air from the drainage system from entering the building under working conditions” and Section 1: 1.3.
NB: to clarify a popular misconception the term “air break to drain” should not be confused with type AA, air UK, B or any other types of “air breaks” found on the cold/hot water supply side of the pipework. An “Air break to drain” is specifically an air break between the wholesome water and the category 5 foul drain, thus the size and open area of the “air break” is determined by a formulaic calculation derived from a water regulations based technical sheet (see 1/ above).
We therefore have several regulations to comply with. Current manufacturer’s installation instructions predominantly leave the issue of connecting the tundish outlet to a suitable point of discharge up to the installer. To be fair, that part is not the manufacturers’ responsibility, but it has led to an alarming number of non-compliant installations.
The most common fault found with non-compliant installations is that of hard piping the PRV discharge directly to waste or drain.
This is an unfortunate and much used installation method and transgresses the regulations in several critical ways:
1 There is no visible means of discharge – No warning that there is something wrong with the installation.
2 Undue consumption, if the PRV is passing continually and no one knows it’s happening.
3 There is no air break to drain, therefore, according to the regulations there is a real risk of contamination to the wholesome water in the cylinder, if the waste pipe blocks and backs up.
All three issues mean that the water supplier and/or building regulator (Building Control) can enforce the regulations and insist that something is done.
Up until now, there were very few affordable and known solutions. The water supplier was reluctant to fully enforce compliancy by asking to fit a tundish because of the issues of smells (which then becomes a building regulations issue).
I’ve designed a product to help with this solution that has full WRAS approval, which can be fitted in the tightest of spaces and with minimal alterations to existing pipe works. It affords the customer and installer an effective and cost effective solution, it has everything built in, including an air break to drain, visible means of discharge and a mechanical odour seal.
It is a requirement of building regulations that there is a drop of 300mm of straight pipe below the tundish outlet before the first bend and that the material used for waste pipe is able to resist the effects of temperatures expected.
Please note that a compliant installation can include the PRV discharge from the cold water side of the installation, therefore it can be argued that there is not expected to be high temperatures discharged from the PRV, so solvent weld (or push fit) waste pipe could be used and be compliant.
Every installation must be looked at to see what discharge temperatures are expected and decisions made as to the correct type of material to be used made.
Regulations are there for a reason and every professional installer is supposed to know them, so if you come across a non-complaint installation you can now guide your customer to give them an inexpensive solution.
Severn Trent water fittings regulations manager Ian Mitchell says: “It is a legal requirement for the discharge pipes from the temperature relief and pressure relief valves to discharge in a safe and conspicuous manner.
”To do this safely the discharge pipe can be connected to the waste pipe. However, to avoid smells a trap or check valve is required to be installed – customers have complained of odour when the water in the trap has dried up over time.
”Using a WRAS approved product designed to overcome these problems, when installed to the manufacturers’ guidance, will allow installers to supply systems that should meet the requirements of the Water Supply (Water Fittings) Regulations 1999.”
Russell Armstrong (Mciphe Dip (HV&AC))
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