In article , Cicero writes
Both ABS and MuPVC use the same solvent system.
ABS waste is thin walled, scratches easily and is the cheaper, low grade product but it is adequate for domestic use.
MuPVC waste is thicker walled, less easy to scratch and can sustain higher temperatures in use. It is specifically required for prolonged discharge of hot water where ABS would soften and start to flop about but is not generally required for a domestic situation. Its higher temperature resistance makes it suitable for use as a flue for compatible boilers such as the Keston range.
Both ABS and MuPVC wastes were specified under BS 5255 but have now been given different EN spec numbers which is sensible considering their different properties.
The sheds used to stock MuPVC exclusively so all my stuff is done in that but on returning to buy some additional supplies at the B&Q I have noticed that the stock seems to have switched the lower cost ABS with a few odd fittings of MuPVC being sold from ABS part bins. If I want MuPVC now it will be easier to go to a specialist drainage merchant where I know I will get the right stuff.