Regulations applicable for pressurised Unvented Hot Water Installations (UVHWH)

Water Regs Compliant Stamp
Building Regs Compliant Stamp

It is well understood that any unvented hot water heater installation connected to the water undertakers (Water Board) water supply has to comply with the Water Supply (Water Fittings) Regulations 1999 and more widely, a pressurised unvented water heater also has to be installed in accordance with The Building Regulations (2010) Document G and Document H (2000)

Initially, when the UK allowed the use of unvented water heaters, amongst the safety features required, that on all unvented cylinders, there needed to be installed a pressure relief valve (prv). The water regulations generally demand that any fittings or installations do not lead to excessive consumption. As such if the water heater develops a fault water which results in an over pressure situation water will be discharged via the prv to drain.

It is very important that an end user has the opportunity to see the water being discharged because it acts as a warning that there is something wrong with the installation. If the installation does not have a visible means of seeing this discharge if left unresolved, not only will there be undue consumption but a catastrophic failure could eventually occur and the building become flooded (or worse).

The regulations were written to address that situation and if the discharge water was routed through a standard tundish in a “safe and conspicuous manner” and was then piped to a safe point of termination outside of the building envelope the installation would satisfy the requirements. However, latterly it was accepted that the discharge water could be terminated to a local soil or waste pipe provided that “it could be demonstrated that the pipework could withstand the effects of the temperatures expected” and that an odour trap containing a “mechanical seal not incorporating a water trap” was incorporated.

In this instance we are concerned with the requirements enabling an installation to be fully compliant if you choose to discharge the PRV to a local foul soil or waste pipe. In doing so we have to concern ourselves with both sets of regulations at the same time plus additional regulator fittings standards. In all, there are 7 requirements that need to be followed to have a fully compliant installation, therefore the following requirements/regulations should be followed;

  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) “….constructed and installed so as to resist the effects of temperature….”
  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.

RA Tech UK Ltd understand these principals and have specifically developed hotun to comply with the above regulations as an all in one unit. Therefore when you fit hotun you know you’ll be doing the right thing and it will be the most cost effective way of doing so, saving you time and money!