Thermal bridge of copper overflow pipes

[Seeoda]

Hi all,

 

I have a gas boiler overflow pipe that runs from the external wall into my 'thermal envelope', behind my kitchen cabinets. It is only a small pipe but I live in a very windy exposed area and copper has phenomenal conductivity abilities so I figure this is a thermal bridge that I should look at. Has anyone ran such a detail through SAP, PHPP or DEAP? Ideally I'd replace the pipe with a non-conductive material but that may be unrealistic? So idea is to insulate both sides Does anyone have any suggestions as to what insulation would work here? It would have to be weather tolerant, heat resistant and hopefully look smart.

[JohnMo]

Do you need to through the wall?

 

Insulated the internal  and external part of the pipe.

 

Can it not go into  a sink drain for example instead of outside?

 

If that's the only thermal bridge to worry about your doing well.

[Radian]

What do the boiler manufacturer's installation instructions say about what you can do with the PRV pipe? Sometimes the MI's have some useful tips.

[Seeoda]

On 08/12/2021 at 15:19, JohnMo said:

Do you need to through the wall?

 

Insulated the internal  and external part of the pipe.

 

Can it not go into  a sink drain for example instead of outside?

 

If that's the only thermal bridge to worry about your doing well.

That is a great point. I honestly had no idea that these could sometimes be run internally. Just to clarify. It isnt an overflow. I think it is a pressure release valve pipe.  It seems with certain plumbing this can go indoors which could also offer the benefit of no freezing risk. I will call Ideal boilers to check exactly what the situation is. 

[PeterW]

It is the pressure relief blow off and must be made of copper or a similar material and must go to an outside wall. 
 

Thermal bridge is negligible - it’s also sealed into the end of a valve on the boiler so no air flow. 

[JohnMo]

1 hour ago, PeterW said:

It is the pressure relief blow off and must be made of copper or a similar material and must go to an outside wall. 
 

Thermal bridge is negligible - it’s also sealed into the end of a valve on the boiler so no air flow. 

It may just be the condensate drain, my combi does not have an external connection for a PRV.  My instructions explicitly state pipework must be plastic.

[wozza]

6 hours ago, JohnMo said:

It may just be the condensate drain, my combi does not have an external connection for a PRV.  My instructions explicitly state pipework must be plastic.

 

Condensate pipe must be plastic due as the condensate can be corrosive.

 

I have a Copper mushroom on my boiler blow off -  very flush looks tidy - most fitters use a couple of elbows to return the pipe outlet to face the wall so any hot / pressurized water is not likely to hurt anyone.

Edited December 10, 2021 by wozza

[Seeoda]

On 10/12/2021 at 10:45, PeterW said:

It is the pressure relief blow off and must be made of copper or a similar material and must go to an outside wall. 
 

Thermal bridge is negligible - it’s also sealed into the end of a valve on the boiler so no air flow. 

 

They have to run off even if you have something like this? https://hotun.co.uk/benefits-of-hotun/prv-discharge-pipe-routing-issues-hotun-the-simple-solution/

As you say, the thermal bridging is bound to be small.

[PeterW]

Yes that is ok but you need to run into the correct pipework as standard polyethylene waste pipe does not meet the standard required under G3. 

[MJNewton]

On 10/12/2021 at 09:45, PeterW said:

It is the pressure relief blow off and must be made of copper or a similar material and must go to an outside wall. 

 

Are you sure? Our PRV discharges to an internal soil stack via a length of copper pipe to a tundish, HepVO valve and 32mm 'plastic' (not sure of actual material/markings) waste pipe to an internal soil stack. I believe it is quite a common setup these days.

[PeterW]

Just now, MJNewton said:

Are you sure?

Yes … if it goes through the wall then it has to be copper. 
 

If it goes to an internal / tundish arrangement then there are various rules including the lengths and type of pipework. 

 

 

Those BS/EN standards are not on all pipes. They don’t apply to a lot of standard polyethylene pipework. 
 

 

 

 

[MJNewton]

Apologies - I misunderstood what you were saying. I read it that you must discharge externally.

[Nickfromwales]

6 hours ago, MJNewton said:

Apologies - I misunderstood what you were saying. I read it that you must discharge externally.

You do in every instance where there is existing foul / waste pipework that you cannot confirm the type / specifications of. If in doubt, pipe goes out.

As @PeterW says, the boiler PRV is a normally closed valve so no through draft can occur, and if you're that worried about this rather insignificant cold bridge, just cut the pipe off inside, drill back through at 25mm diameter and push a 21.5mm pvc overflow pipe into the wall as a sleeve. Seal that both ends with a suitable sealant.

Re-fit the 15mm copper pipe through the sleeve, and fill the gap around the copper pipe with expanding foam at both ends.

Problem ( if one actually exists ) solved.