PVC waste pipe to copper

IME the transition / compression waste fittings seem to cope well with mismatched pipe diameters when going between push fit and solvent weld - so if you can get the copper in there, it ought to work.

(having said that I can't see that proximity to radiator pipes is going to have any effect on the waste pipe - you can pour boiler water down a waste pipe without it deforming)

Hi John Since posting I did check out the McAlpine website and it did say in the specs that the compression fittings do fit the standard copper pipe sizes and quoted a relevant standards number that off the top of my head I cannot remember which I suppose applies to all copper pipes in the UK.

I take your point about the boiling water, I am a little concerned that under sustained heat by a radiator deformation could take place having seen how PVC waste pipes can be deformed with a heat gun. I suppose the practical thing to do is “suck it and see”. I can always graft in a section of copper pipe if I have to, it was just a case of confirming the fittings ability to transition from plastic to copper by someone who has done it before rather than find out at a later point there is a problem.

The price of 42mm copper tube might be interesting, I noticed a 6m length for £160

Which on low temp will still likely exceed 200 deg C... I doubt you boiler is going to get the water that hot (and if it does I think you have more pressing issues than a warped pipe!)

Or stick a bit of insulation between the plastic and copper...

I have never made a joint to copper that large, but would expect it to work sice it does on other sizes and the principle is the same.

I found one source @£42 + VAT for 1.5m which is one of the reasons I want to be sure it works before committing.

I wonder if it might be a duration problem? If boiling water is flowing through a waste pipe, it passes through and leaves the pipe empty on completion. If the waste pipe is positioned close to a radiator, it is subject to heating from the radiator for hours at a time, and it will be only holding air for nearly all that time. I don't imagine a waste pipe will be designed for such a scenario. The OP is being sensible for trying to avoid it being a problem.

Oh FFS. Domestic Radiator max temp 60°C. Copper solder joint unsolders at 180°C Waste type PVC good up to *at least* 60°C. Special plumbing smaller bore PVC plumbing pipe about 82°C-90°C

If it was near a trap I might agree. Otherwise, I'd let it go.