DIY Doctor

Main navigation

Sealed system safety valve venting requirements - need help.

Postby corkee » Sun Aug 05, 2007 11:52 am

Could someone advise me what the usual venting/drain arrangements are for a safety valve fitted to the expansion vessel/pressure gauge assembly?

All I know is it has to be sized to suit the expansion vessel supply pipe, in my case, 15mm. (Fed from a 22mm/15mm reducing tee near the pump inlet).

I've seen some layouts which seem to have a captive tundish (presumably to serve as a warning function) see: ... 0Extra.pdf
but I'm not at all clear on where it should be vented to.

Could it be acceptable to use 15mm Copper tube into a catchpot? - I assume it's only ever going to vent a small quantity of water from a fixed volume sealed system?

Alternatively, can it be vented into an existing drain (eg boiler condensate)?

Thanks in advance.
Rank: Apprentice
Progress to next rank:
Posts: 7
Joined: Sun Aug 05, 2007 11:38 am


Simply Build It

Postby htg engineer » Wed Aug 08, 2007 9:19 pm

Pressure relief discharge pipes are normally taken to outside via a 15mm copper pipe. They have to point towards the wall away from pedestrians, windows, doors etc.

You shouldn't get any water coming out of this pipe unless there's too much pressure or a fault on the system, then there'll be alot of water distributed through this pipe not just a small amount.
htg engineer
Rank: Project Manager
Posts: 3256
Joined: Tue May 22, 2007 5:22 pm

Postby corkee » Mon Aug 13, 2007 8:38 pm

Thanks for that,.
I am thinking of feeding say, 1 metre of 15mm Copper pipe from the relief valve outlet into the old 22mm overflow pipe (from the now redundant F&E tank) and adding an elbow at the outside end to turn the outflow towards the wall.

My thinking being that the gap between the 15mm and 22mm pipes will serve a similar function to a tundish, ie act as an air break

Think this will be OK? or are there issues with using plastic for pressure relief purposes?

Rank: Apprentice
Progress to next rank:
Posts: 7
Joined: Sun Aug 05, 2007 11:38 am

Display posts from previous
Sort by
Order by

  • DIY How to Project Guides
  • DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!

  • Related Topics