Condensate and PRV outlet pipes

[iep]

I'm moving a boiler from a kitchen up into a loft. As a result will need to re-route condensate pipe and go from an open vent to a sealed system (no space for F&E tank above boiler). So, will need a new expansion tank and PRV (with outlet pipe for discharge).

What are the regs for routing these outlets (condensate and PRV discharge)? Easiest would be to route them out the side of the house but I suspect I'd not be allowed?

Cheers,

iep

 

[wayneatatag]

If you fit a ATAG boiler, they have a combined pressure relief and condesate outlet. The condensate runs as usual to a suitable drain point. If running this outside suggestr doing so in 35mm plastic pipework to help avoid freezing

 

[iep]

Thanks but we're moving an existing (nearly new) open vent boiler. Just need to know how to route the condensate and PRV outlet pipes.

Good point RE combining the two pipes and running a single one outside. Do I have to run this down to ground level (like PRV from unvented cylinder)?

Natch, am only planning all this so I can pre run the pipes before boxing in walls in loft. Plumber will do the actual boiler move work.

iep

 

[petit_pablo]

First question - what boiler?

If its suitable to be fitted on a sealed sytem then guidance will be given in the manufacturers instructions as to how to do it.

Condensate will need to be taken to a waste drain, PRV termination will need to be visable in a position that will allow safe discarge.

 

[iep]

Always hesitant to name a boiler on this forum since it usually results in the thread descending into a series of other people's horror stories but here goes. It's a Viessmann 100W compact.

Definitely suitable for a sealed system (according to the manual).

I'd heard that condensate can simply be run to a pipe out the side of the building rather than via a proper waste drain (hence all the freezing issues in winter)? Not a disater if I have to route it to a drain but easier to terminate through an outside wall.

PRV termination. I guess what I am asking is what constitutes a position that will allow safe discharge.

 

[petit_pablo]

Condensate ideally should be run to the internal waste to prevent freezing. No issue with running the pipe outside to an external drain just be aware that it could freeze and size accordingly. 35mm and/or lagged.

PRV termination needs to be outside the building.
The pipe can then either be turned back to the wall at any height so any discharge will spray the wall or it can be taken down the outside of the building so that it terminates near the ground <6".

BuildingRegs doc. G3 gives better guidance than GSIUR or BS's on discharge terminations.

 

[iep]

Great advice thanks. Come to think of it, I've seen a few of these 'turned back on themselves' vents on a block of flats near my work. Now I know that they are.

Cheers,

iep

 

[longdogs]

My boiler is in the loft and the condensate pipe runs outside and into the guttering down pipe. It is lagged and has survived the last few winters ok.

 

[Phill Peck]

Normally your soil pipe will go through your loft so you can take your condensate there

The prv will need to go outside and terminate in a visible possition

 

[mickyg]

what did the installer say?

 

[MJN]

PRV termination needs to be outside the building.

That's not true. Indeed, it is becoming increasingly common for PRV's to terminate internally, usually via a turndish and Hepv0 valve into a soil stack.

Mathew

 

[holty]

viessmann will allow the prv and condensate to be combined. the new wb1c out in the summer is designed for this purpose with combined prv and condense outlet. good boiler shame about the pump flow switch.

 

[kirkgas]

Normally your soil pipe will go through your loft so you can take your condensate there

The prv will need to go outside and terminate in a visible possition

this is ok if the soil pipe is plastic, but if its cast iron the condensate needs to be joined in the wet area, not in the dry vent section

 

[Phill Peck]

Normally your soil pipe will go through your loft so you can take your condensate there

The prv will need to go outside and terminate in a visible possition

this is ok if the soil pipe is plastic, but if its cast iron the condensate needs to be joined in the wet area, not in the dry vent section

That is true
I don't see many cast iron soil pipes TBH

 

[drbagiva]

viessmann will allow the prv and condensate to be combined. the new wb1c out in the summer is designed for this purpose with combined prv and condense outlet. good boiler shame about the pump flow switch.

FYI..............

Pump flow switches have not been used on Viessmann boilers since 2008. Not that they were ever a problem anyway! (only when they get blocked with system debris, overheating is now prevented by an flue temp. sensor)...... Neither have mechanical DHW flow switches on 100 series (now uses a reliable electronic sensor) and diverter valves since 2008 have been bullet proof.