Can unvented cylinder discharge be connected to this overflow?

[aleant]

Hi,

I'm looking to install an unvented cylinder in my property.

I initially hired a plumber who expressed interest in the job, but later cancelled, citing "building regulations" as the reason, specifically regarding the discharge pipe and its location.

Subsequently, I reached out to my second choice plumber to inform them about the issue. However, they claimed that there was no problem in utilising the existing overflow piping (indicated by the purple arrow) for the unvented cylinder discharge.

I would appreciate your input on which plumber's advice is correct. Ensuring a safe install is my primary concern.

Some images of the current vented cylider:

Image hosted at ImgBB

Image Image hosted in ImgBB

ibb.co

IMG-8870 hosted at ImgBB

Image IMG-8870 hosted in ImgBB

ibb.co

Thank you.

 

[Timmy D]

G3 regs (unvented cylinders), state that the d2 section of discharge pipework (connects the tundish to final point of discharge), must be capable of handling the temperature (+/-100c).

Typical waste pipes are upvc (which your arrow identified pipe looks to be) which is not rating for these potential high temperatures.

High temp rated pipes that are typically used are:
Copper
PP (polypropylene) pushfit
Mupvc waste pipe (high temp rated waste pipe)

I’m addition to the d2, the soil stack also needs to be able to handle the heat.

So, without confirming the material of your waste pipe, I can not say for certain if it’s ok, but I doubt it.

If you look at a fitting, it should indicate the material.

 

[exedon2]

If you look closely that old pipework is clearly marked hunter overflow pvc.
So I leould say that's a no.

 

[king of pipes]

Sorry I agree no that's only suitable for use as a overflow pipe. Kop

 

[Ben-gee]

Nice spot exedon2! Eagle eyes.

OP - yes your first plumber was correct, you can’t use that pipe.
However you could use the route that it takes and replace it with a suitable alternative (copper is my favourite. May need to be upped to 28mm depending on how far it has to go) - this is assuming that the termination is suitable…

Whichever plumber you use they must be G3, I’d steer clear of the 2nd one if I were you…