40mm pushfit

Pushfit pipes are *not* interchangeable, not necessarily even between brands. If the pipe you bought is for compression fittings the best thing you can do is get the correct pushfit pipe for the runs either side of your pushfit joint. Compression fittings will probably seal to it adequately, they are not so size critical.

"40mm" pushfit is generally 40-41mm OD, solvent is about 43mm OD, is the

I though it would be like copper pipe, mix and match. Weld most of the sections and then use compression for a tricky joint. But nope.

It would be interesting to know why.

No, in fact they are deliberately made incompatible since you need different types of plastic for the two different applications. The push fit normally needs a softer more elastic polypropylene pipe, while the solvent weld uses a more rigid ABS pipe that will also melt with the solvent.

The only way you can transition between push fit and solvent weld is with the "universal" compression fittings.

OK thanks all - I assumed wrong. The pipe is actually solvent-weld type but is fine with compression joints. It's just the "38mm" pushfit elbow that doesn't fit.

The ones sold for compression are nothing special, just cheaply made and moderately expensively sold, esp in diy stores. As I said, you can get couple of lengths of the proper pushfit pipe just for the lengths meeting at your 135degree joint, and the other ends will work with your compression fittings. Altenatively, of course, you can get the right make of 135degree solvent weld bend, but not if you ever want to be able to dismantle it without replacing the pipes.

The chrome trimmed fitting for where the waste pipe of one of our washbasins passes through the tiled floor fits the underfloor piping perfectly, but the vertical, chromed plastic pipe feeding down into it was too large and I was unable to change to something else as then it wouldn't fit the trap and elbow! I ended up heating the chromed plastic tube and forcing it into hole drilled into a piece of wood to reduce its diameter.

SteveW

THAT is a neat trick I will remember.

Trust me, it is better now than it used to be when they first came in. The modern "compression" fittings with a screw fitting and chevron seal may be bulky, but they cope better across "pushfit" pipe from different sources. (Recognising that they come in "sink" and "bath" sizes of course).

An example of modern quality.

The standpipe appears to be push fit. At least, I couldn't replace it with a solvent weld pipe. The bottom compression joint was fine with solvent weld.

There must be a word for the opposite of swaging. When I did the bathroom in solvent weld, I was about 3" short (yes, I've had that complaint before ;-) )so swaged out the pipes and inserted a small offcut.

Crimping?

No - that puts wrinkles in it. I'm thinking of trying it on a piece of pipe that's just an awkward fit - too small for 40 mm compression (which I want), too big for 32 mm - I'll try to warm it up and get 40 mm push fit over it. Can't afford to increase the dia. of the 40 mm. Luckily, I picked up on impulse a heat gun fro Aldidl last year.

Oddly, the definitions I've seen for swaging all refer to reducing the diameter, but I've always known swaging to be used to refer to increasing or decreasing the diameter. If you want to specifiy which, simply using swaging-up or swaging-down.

SteveW

Didn't know that. I used swaging as a method for joining refrigeration pipes, but those are thicker than water pipes (also work on ID, not OD). It's a very sound method: swage, clean up with steel wool, insert, Cuproflo(?) with oxy-propane (no flux) and a very strong joint in about half an inch of pipe.

Yup same here, although I have quite often heard the use of the term "flaring" for making wider...

Isn't that just making a conical taper for a compression fitting like brake pipes?

Yes - and refrigeration pipes (don't forget the backnut!).