Pressure relief pipework

[Nat]

Hi all,

Bit of advice please...

Went to look at a combi changeover job today and the boiler is hung on an internal wall inside a cupboard off the hallway, the patio door is on the other side of the hallway. The PRV pipework runs into the washing machine standpipe for the w/m next to the boiler. This isn't allowed, is it?!

My question is where to run the PRV? There is a cloakroom toilet next to the cupboard - is it allowable to go into the 4" for the toilet. I know this sounds odd but this is allowable for an unvented cylinder and I have done this many times so can you do this with the PRV from a combi?

Cheers,

Nat

 

[SimonG]

Probably need a hepvo waste and a tundish. Never had the problem as I always get it outside, lucky I suppose.

 

[dancinplumba]

you will need a tundish and a trap, you can run yor condensate ito w/machine trap.
steve

 

[Kerr Gas 1]

Hi nat,

this is a question i asked a couple days ago as i was fitting a 28i junior in a cupboard where i had no external wall close to run my prv. i got a couple of mixed replies, some stated its perfectly fine as long as there is an airbreak between pipe and discharge point, some sayed that the prv determend where the boiler is fitted as it must run directly outside. i ended up discharging it into the wash machine stand pipe in the end but as soon as i get word back from building control whether this is acceptable or not will determine if i have to change it. i beleive there is a pump on the market now that acts exactly like a condi pump maybe thats an option???

 

[Nat]

Hi nat,

this is a question i asked a couple days ago as i was fitting a 28i junior in a cupboard where i had no external wall close to run my prv. i got a couple of mixed replies, some stated its perfectly fine as long as there is an airbreak between pipe and discharge point, some sayed that the prv determend where the boiler is fitted as it must run directly outside. i ended up discharging it into the wash machine stand pipe in the end but as soon as i get word back from building control whether this is acceptable or not will determine if i have to change it. i beleive there is a pump on the market now that acts exactly like a condi pump maybe thats an option???

Interesting. Thanks for your reply. So you ran it into washing machine standpipe as I found in this installation. Would be nice if this was allowed but I doubt it is. I know from doing unvented cylinders that you can run the PRV into tundish, hepvo and high temp plastic with push fit fittings into 4 inch and I don't see why you couldn't do this with a combi.

If anyone else has a definite answer for me I'd appreciate it. Going to phone Gas Safe tomorrow and see what they say.

Thanks for all your replies

 

[Mbear]

Its always been my opinion that the discharge point should be visible/outside. Could u not cap the boiler prv pipe and rig up one on the system where it's accessible for repair and close to an outside wall so the termination is visible. The annoying thing about a safety pipe term not being visible (for a repair guy anyway) is that u obviously can't see If the valve is passing or not. If u did decide to fit a system prv I'd leave some sort of label on the chb indicating where the working prv is fitted, just incase a future engineer opens a can of worms when in reality everything is safe and correct

 

[dancinplumba]

hi, thats what the tundish is for...
steve

 

[dave99]

all PRV`s are set to blow at 3 bar pressure and may discharge hot as well, so a open ended wash/mc up stand [which normally have a built it trap ] would not be able to cope with discharge at this pressure/heat which could lead to flood of hot water at 3 bar out of up stand .not good idea .
d99

 

[Mbear]

all PRV`s are set to blow at 3 bar pressure and may discharge hot as well, so a open ended wash/mc up stand [which normally have a built it trap ] would not be able to cope with discharge at this pressure/heat which could lead to flood of hot water at 3 bar out of up stand .not good idea .
d99

I've been doing this a long time and I've never seen a ch prv 'blow' as ppl say. Dribble and drip maybe but never blown. I do agree with u though but for slightly different reasons matey

 

[dancinplumba]

an thats why you use hepv0 valve, its accepted.
agree mbear

 

[Napper]

i suppose someone could leave fill loop connected and nock tap while system hot. that may make it blow hot, needs to be customer proof!
no ive never done it:thinking:

seen commercial temp/prvs go most recently 2" on a biomass boiler - made me jump!

 

[Nat]

OK so I spoke to Gas Safe and Worcester Bosch today and they both said that putting a PRV to discharge into a standpipe is definitely NOT acceptable. I looked on the Hepv0 trap website and they do not recommend using a Hep trap for a boiler PRV but it is definitely OK for an unvented cylinder temperature and pressure relief valve - I am not sure why one is acceptable or not.

I think I have found a solution though:

Boiler Buoy:Condensate Pumps

Apparently you can fit one of these pumps then take a hose to a strap on on the soil stack and this is acceptable according to the manufacturer. Thing is this costs £300! Also I don't see the difference between this and running a bit of polypropelyne pipe to the stack.

Can anyone make sense of this?

 

[gaspastemania]

I spoke to gas safe before about blow off terminations and they said nothing to do with us speak to building control lol Talk about slopey shoulders !!!

Lets be honest who can make sense of it all can use hepvo trap on one cant on another yet i have used them on boilers and been inspected by gsr and build control and only thing they mentioned was building control want the traps vertical .

 

[AWheating]

seen hundreds of boiler blow off's run into waste systems, mostly on flats. It is def a building control issue if anything.

 

[Nat]

Found a solution to this problem: Atag boilers.

They have no PRV pipework at all. The boiler modulates itself down if the pressure gets too high and any water that is discharged, as it's so little, can go down the condensate run. Clever stuff!