Unvented cylinder discharging into soil stack

[myrica]

Hi all, hoping that someone can help. I know similar questions have been asked a zillion times on forums, but I can't find a definitive answer for my bit of the equation.

I believe an unvented cylinder can be discharged into a soil stack via a tundish, a Hepworth trap, and via suitable polypropylene push-fit pipe certified to higher temperatures etc. I've read the english and scottish guidance, the NHBC technical guidance, and various manufacturer's installation instructions.

What I cannot find out, is more specifically what material the soil stack needs to be. The G3 regs say "the discharge pipe should not be connected to a soil discharge stack unless it can be demonstrated that the soil discharge stack is capable of safely withstanding temperatures of the water discharged", and I found something else suggesting this is at least 100 degrees.

So what material (other than cast iron) fits the bill? I have a (presumably fairly standard) internal PVC soil stack. Discharging externally isn't ideal for various reasons.

I should say I am not a plumber and I am not looking to do any work myself. I am a homeowner who likes to be as informed as possible, and I am trying to work out whether what has been proposed to me is up to code.

Any help or advice would be greatly appreciated.

 

[Nige F]

75 degrees max continuous - greater temp. limited to 2 minutes. From Marley Soil FAQ.

 

[myrica]

"Although they are tested at 93.0 to 95.0ºc {British Standard test} this is an intermitted hot and cold cycle test. For a continuous discharge, water should be no hotter than 70 to 75ºC. Higher temperature water will not cause problems as long as it is restricted to 2 minutes discharge."

Which suggests my existing PVC soil pipe cannot be "demonstrated to safely withstand the higher temperatures"?

Assuming that in the event of a fault, it could/would discharge for more than the 2 mins, which presumably depends on what the fault is that might cause it to discharge.

 

[PullerGas]

The High Temp PP push fit is all that's required for your D2.
Standard UPVC is fine for the 110mm soil pipe.

It'll only discharge at a drip rate or slow trickle at worst.

ANYONE WORKING ON UVC.....must be G3 qualified, it's not a DaftyDIYers job!!

 

[myrica]

Thank you. It sounds like you agree with what my plumber is suggesting. I have had some conflicting advice from another plumber. Both are G3 qualified.

But also, as I said, "I am not a plumber and I am not looking to do any work myself", so no shouty capital letters required thank you very much. Keep your hair on