wickes 40mm waste pipe... 43mm

Someone will doubtless come up with more on the standards (or lack of them) but having suffered from the same problem you might look for the word "universal" on plastic plumbing fittings in the sheds or wherever. These have more "slop" and a big fat conical sealing washer which fits various pipe sizes.

Apart from the nominal 1 1/4 and 1 1/2 inch ("sink" and "bath" waste pipe) which goes into "compression" type fittings with rubber seals, there are also solvent weld pipes.

Personally I would have said you have a strong case for a refund given the clear mismatch between the labelling/receipt and the product.

The normal gotcha with waste pipe is that push fit/universal is a different OD to solvent weld. Just measured some solvent weld at 43mm OD.

Forget about metric sizes for waste pipes; it's confusing. There are only t wo sizes of waste pipe: inch-and-a-half and inch-and-a-quarter. That's it. Forget about compression fittings; they're for wankers. They confuse the pi cture further by being slightly different diameter to solvent weld. More co nfusion comes in (with mm) when manufacturers specify the outside diameter instead of the inside and vice versa. In summary: Forget the sheds. Only ever go to a plumber's merchant and get either inch+ half or inch+quarter solvent weld only and you won't go wrong.

sizes of waste pipe: inch-and-a-half and inch-and-a-quarter. That's it.

What about 2 inch?

...

inch+half or inch+quarter solvent weld only and you won't go wrong.

Except even they are not always compatible.

Colin Bignell

Ahhhaaa, that could well be it, the 43mm pipe seems to be a different type of plastic to the 40mm one, it's more like electrical conduit pipe, so it could well be solvent weld pipe after all,

I personally buy pipes from a builders merchant close to me, but my parents seem to not want the 'hassle' so pay over the odds at the sheds, plus he bought it on a sunday afternoon as he wanted the job finished.

The solvent weld stuff seems to be harder and more shiny than the push fit stuff in my experience. I prefer solvent weld personally, once it is installed, then it is there forever!

Solvent weld is deliberately made a little bigger. It will fit solvent fittings and "universal" (i.e. compression) fittings. Sounds like the trap was a push fit one. That's smaller and a slightly softer plastic.

The pipe sizes vary between manufacturers. This means that push fit (O ring) and glueable pipe fittings are non- interchangeable.

However the compression fittings fit everything but are more expensive. They are dismantleable for if you get a blockage which is good.

A blockage is good?

sizes of waste pipe: inch-and-a-half and inch-and-a-quarter. That's it. Forget about compression fittings; they're for wankers. They confuse the picture further by being slightly different diameter to solvent weld. More confusion comes in (with mm) when manufacturers specify the outside diameter instead of the inside and vice versa.

inch+half or inch+quarter solvent weld only and you won't go wrong.

That may be true if you are buying all your pipe and fittings in one go.

But it's definitely *not* true if you need pipe to marry up with push-fit fittings - as the OP found to his cost!

or inch+quarter solvent weld only and you won't go wrong.

Bingo.

If you have the runs, yes.

Same happened to me - bought "40mm" pipe (marked on Screwfix label as 40mm) only to find that it was 43mm (printed by manufacturers on pipe).

This is when you need someone with experience. There are 2 types of 40mm pipe, push/compression fit, and solvent weld.

Solvent weld is wider than push fit, and they cannot be interchanged. There are some compression fittings that will accept it. The 40mm is the internal diameter.

Yes, indeed - this crops up from time to time here - and is a trap (sorry!) waiting for the uninitiated to fall into.

Yes isn't it!, just think they'd err umm standardise on things like that;!...

There are: inch-and-a-half and inch-and-a-quarter (solvent weld). Anything else is BS and/or a red herring.

Well they *have* insofar that push-fit and solvent weld pipes are a different size to prevent the wrong combinations of pipe and fittings from being used. The only problem is that they're both *called* the same

- at least at first sight.