PRV discharge pipe routing issues -

PRV discharge pipe routing issues – hotun, the simple solution

PRV discharge process

It is essential that, on a sealed heating or unvented hot water system, any PRV discharge can be observed and that passing water is safely directed to a point of discharge. This can be difficult for installers working in landlocked or high-rise installations where points of termination can be limited to long individual runs down the inside of the building to a basement level gully.

The hotun dry trap tundish is fully compliant with building and water regulations. hotun differs from the traditional tundish with its ability to eliminate foul odours without risk of drying out. This one product solution solves many of the boiler or unvented water heater (T)/PRV discharge routing issues installers are commonly faced with.

If there is an internal, foul waste or soil pipe available near the boiler, then using the hotun dry trap tundish could be your most cost-effective and compliant answer.

PRV discharge pipe routing issues -

PRV discharge pipe routing issues

A traditional tundish allows water from a PRV discharge to pass through the tundish and enables the user to observe this from its open-sided construction. Complications occur for installers in these high rise and landlocked situations as they have few economical options to terminate the discharge pipe. If a standard tundish were to be fitted they cannot terminate to a foul waste or soil pipe as foul odours are able to travel back up to, and out of, the tundish to the inside of the building! A definite no, no in terms of regulatory compliance.

A wet trap cannot be used, as the infrequent operation of the PRV would allow the wet trap to dry out and become ineffective!

Boiler PRV discharge pipe – how to stop odours with hotun

The hotun dry trap tundish has been purposely designed to help resolve PRV discharge pipe issues. It preventing smells from traveling back up from the drain connection. The hotun tundish follows the same design of the standard tundish with an open-side. This benefits the home owner because it allows them to witness any passing of PRV discharge. The design of hotun includes a patented non-return valve. This valve comprises a one-way sprung valve that closes shut to protect against odours and then when water is present (between 5ml and 30ml), the sprung valve is triggered and opens to allow the water to pass through.

Boiler PRV discharge pipe - how to stop odours with hotunPRV discharge pipe issues resolved with hotun

Boiler pressure relief valve discharge pipe – how to combat limited points of discharge with hotun

The hotun hiflo tundish can be used to help combat limited options for installers working in landlocked or high-rise locations. It is now possible for the PRV discharge to be directly connected to the internal waste. The condensate drain can be connected below the tundish.

Ideal Boilers give advice on how to do this in one of their technical bulletins (AD 117), this hotun installation guidance tells you all you need to know.

Boiler pressure relief valve discharge pipe - how to combat limited points of discharge with hotun

  1. Internal boiler condensate trap
  2. 5mm condensate pipe (must always Tee in below tundish outlet)
  3. 32 – 22mm rubber reducer
  4. Boiler pressure relief valve PRV
  5. 15mm Copper PRV discharge pipe
  6. hotun shield
  7. hotun hiflo (max 600mm from boiler)
  8. 32mm HDPE/PP waste pipe
  9. 32mm universal HDPE/PP waste T fitting

Typical compliant installation options for boiler PRV discharge to drain via hotun dry trap tundish

Typical compliant installation options for boiler PRV discharge to drain via hotun dry trap tundish

Typical compliant installation options for unvented hot water cylinders T & P and PRV discharge to drain via hotun dry trap tundish

This article discusses PRV discharge from boilers. Happily, our hotun dry trap tundish can also be used for unvented water T/PRV discharges. Because of the way T/PRV operate verses a PRV (from a boiler for example) there are specific installation details that need to be adhered to. To make sure the installation is compliant with Water and Building Regulations, please read our Manufacturing, Maintenence and Installation Instructions

Typical compliant installation options for unvented hot water cylinders T & P and PRV discharge to drain via hotun dry trap tundish

Benefits of hotun

The hotun dry trap tundish provides installers with a solution to PVR discharge issues that is quicker, easier and cheaper than alternative methods whilst being all under one fully compliant unit. A comparison of the hotun product against other current compliant installation options including average money savings can be found below:

hotun dry trap tundish- solutions to PVR discharge issues

Benefits of the hotun include:

  • Small-sized and ideal for use in small spaces
  • Users are able to visibly see the PVR discharge. Please note, that ANY dripping water is a warning that something is wrong with the system and expert assistance is required
  • Ability to deal with trickle and full flow discharge conditions
  • hotun & hotun SF 15 – 22 has a flow capacity of up to 16 liters/minute
  • hotun hiflo & hotun hiflo SF 15 – 32 has a flow capacity of up to 25 liters/minute
  • Our current largest unit, hotun XLSF 22 – 32 has a flow capacity of 40Litres/minute
  • Compatible with any unvented hot water heater or sealed system boiler PRV discharge pipe
  • Removes the risk of wholesome water supply contamination
  • Eliminates the need for any drilling work through external walls
  • Standard plumbing connections are used on the inlet and outlet

Additional information

The hotun and hotun hiflo PRV discharge products are tested by accredited UKAS bodies and are the only dry trap tundish officially accepted for use by the following:

For further information on boiler applications please click here

For unvented hot water heater applications (under 15 litres capacity) click here

For unvented hot water heater applications (over 15 litres capacity) click here

To buy one of our hotun dry trap tundishes or products please see our trade suppliers list here