D2 Discharge Pipe Materials

[Stigster]

Hi Everyone,

I have been asked by a student if any manufacturers have had their plastic pipe approved for use on the D2 discharge pipe of an unvented cylinder? I know about the HepVO method and using pushfit waste pipe to a stack - provided the stack is able to take this type of discharge - but the student is asking about flexible plastic, like Hep2o or Tectite plastic "flexible metal" barrier pipe.

I have had a quick search on the interwebs but can't find much in the way of a definitive answer. I know the G3 document has said that the D2 must be metal pipe for many years now and then the waterless trap method came along and they changed it to accept that. What about other forms of plastic pipe?

Any insight into this is much appreciated.

Edit to add - I am seeing that any material can be used as long as it can withstand water at 95 degrees Celsius. I see that the regs say -

3.57 The discharge pipe (D2) should be
made of:
a. metal; or
b. other material that has been demonstrated
to be capable of safely withstanding
temperatures of the water discharged and is
clearly and permanently marked to identify

This however does not mention a temperature. Where are people getting 95 degrees from? I see that Tectite Flexible metal pipe (plastic with an aluminium layer) is rated to 95 degrees for instance but that is not just a plastic pipe.

 

[Stigster]

I think I've just worked out something that should have been obvious to me. The T & P valve on all the systems I can think of have a setting of 90-95 degrees to start operating. Obviously that's where the figure of 95 degrees that people talk about comes from. This figure is not to be found in any regulations because T & P discharge temperatures could vary between manufacturers maybe?