Question from Mark Dixon, via e-mail:
Can the discharge from a tundish servicing an unvented cylinder run into an internal soil stack?
Answer from Martyn Bridges, director of marketing and technical support at Worcester, Bosch Group:
The Building Regulations Part G has recently been amended to allow this type of thing. However, there is a criteria to meet, which is quite difficult:
The material that the waste water system pipework is made from must be able to withstand the temperatures and pressure expected from a T&P Valve connected to a cylinder. Generally, this is temperatures of around 90ºC and pressures of up to 9-10 bar, I am not aware of a plastic waste pipe or soil stack system that achieves this. I guess a cast iron system would be satisfactory, however, it is most unlikely that the internal soil stack is of that material.