Overflow pipe - 3/4" vs 21.5mm

[garyo]

I have a long run of overflow pipe that I need to modify. It's stamped '3/4" 19mm'

I've bought some 21.5mm fittings but the existing pipe is around 1mm too wide to fit. Is this usual... do I just need to sand down the outside to get the old pipes to fit the new unions?

I'm confused by the various websites that seem to sell unions as nominal "3/4 inch 21.5mm" when they clearly can't be compatible with both systems?
e.g. https://www.raygrahams.com/products/116157-overflow-solvent-weld-tee-34-215mm.aspx

Thanks

 

[Phill Peck]

You can buy adaptor couplings or file it down.
I'd use an adaptor.

I guess u have floplast from screwfix?

https://www.angliatoolcentre.co.uk/...kK9TZUCjjDOR8XQatZ9A0q0Eua4siWehoCd7YQAvD_BwE

 

[garyo]

I guess u have floplast from screwfix?

Yes precisely. I think I'll have a crack at rubbing one down tonight to see how hard the plastic is. If I use the reducer couplings then I'd need 3 of them and I prefer the clean look of a solvent weld solution.

 

[Phill Peck]

There are solvent adaptors that my local merchant sells but couldn't find them online

 

[polesapart]

It's annoying; OD of overflow pipe does vary with manufacturer.

I can never remember which is which.

Heat usually does the trick.

 

[garyo]

Mmm heat. Now you're talking. I'll get the blowtorch on it.

 

[garyo]

Heat usually does the trick.

Great advice. A tiny lick of the blow torch makes it highly malleable, then it sets hard again. A very neat job. I expect a dip in boiling water would do the same thing (impractical in my case due to some of the pipes being fixed horizontally)