Is it acceptable to use a tundish with only 330mm under the boiler?

Question from Tom Bishop, via email:
Basically I have a system boiler in a loft in the middle of the house. I’ve run the pressure reducing valve (PRV) straight into afour inch waste pipe, which I know is fine, but I don’t know whether to put a tundish on it, as I only have about 300mm under the boiler.

AndI know that you cant have a bend with in 300mm of the tundish. Need help!

Answer from Martyn Bridges, director of marketing and technical support at Worcester, Bosch Group:
It is acceptable to terminate the PRV from some boiler products into a waste water system, but it would be advisable to check this with the boiler manufacturer first.

Once that has been clarified it is important to be able to see whether the PRV is or has discharged therefore a tundish is probably the most suitable product to achieve this result.

The 300mm distance you are referring to is I believe the requirement for the discharge pipe from a Temperature and Pressure relief valve on an unvented hot water storage system, which of course this isn’t therefore I would advise a tundish is fitted and that you leave as long a vertical distance between the PRV and the tundish as you can.

One further consideration is that any materials used in the waste water system must be capable of accepting the temperature and pressures exiting the PRV, again a case to ask the pipe manufacturer once you have confirmed that the boiler manufacturer is happy.