Separating OSMA piping used as ducting for air vents

Its probably solvent-weld so its nigh on impossible to separate. Cut it and replace, its cheap enough. Go to proper builder/plumbers merchant for compatible stuff. e.g. Jewsons, Travis perkins.

Cut it with a saw and reassemble with couplers. The cost of couplers is small compared to the aggro saved.

Owain

If it is push-fit there'll be a bulge near the neck of the collar which contains the O-ring. If it's solvent then the diameter of the collar will be more-or-less the same. If it's push-fit you should be able to twist it: wrapping rubber strips around the sections (or using one of those Boa grips) may help. It may also help to get some washing up liquid or furniture polish spray into the joint.

It's worth salvaging what you can as soil pipe and fittings are pretty expensive, and are reusable. For new stuff you'll probably find Screwfix a lot cheaper than your local merchants.

For vent ducting you can make joints by cutting pipe at an angle, trimming the cuut edges to make a good fit and solvent welding. You need to leave it a long time (like a day or so) with the joint held together e.g. by PVC tape, for the weld to set properly, and may still have to seal hairline cracks with (e.g.) tape or sealant, but it can let you make joints at arbitrary angles without the bulk and expense of 'proper' connectors. (Obviously you don't want to try this when using the pipe for soil!)

Glued usually. Cut, insert couplers and reglue.

It was push-fit AND had a solvent weld on it! I cut through it in the end and bought some new pipe and a 90 degree bend from Jewsons as recommended.

The bend cost =A310.60 and 3 metres of pipe cost =A318 so they weren't exactly giving it away.

Thanks for all the comments.

Steve