O-rings for MDPE fittings - where to buy?

Can't you just extract one and measure it? Buy a spare fitting to destroy if you need to.

O-rings are measured by inner diameter x cross section (then OD = ID + 2*CS)

I presume they will be nitrile rubber (they're not for a chemical factory where you might be more fussy).

There are (of course there are) three different size standards - American, British and metric. You should be able to match up the dimensions with one of the standard sizes.

Theo

You mean this kind of thing:

The description does list BS 7291-1, 2 as a standard - so that would likely give you actual specs.

After Manchester central library stopped allowing access to BS Online, I've used Lancashire libraries for several years, either they've re-organised their website or also stopped providing access, anyone still able to access it?

Well, yes, sort of. However at £1.31 ex vat each I think I'll give them a miss! I'd expect to get a pack of 10, or more, for that sort of price. Certainly 'generic' O-rings are much cheaper. A 20mm x 20mm elbow that will have two O-rings in it is only £2.59 from Screwfix.

I've had a bit of a hunt around but I can't find anything that specifies O-ring sizes.

I can access them with a Lancashire library card number, but the only dimensions are for pipes; resistence to pulling out for fittings.

My bookmark to

fails, their search page doesn't find a replacement, what do you use please?

When you do measure one, lots of them on aliexpress for peanuts

Buy a spare fitting to

Try a proper plumber’s merchant, they sell them for pennies.

Or, if you can wait, watch Lidl middle isle offers. I bought a box of mixed ones for a few pounds. Typically, Lidl cycle special offers every few months.

Yebbut you can almost guarantee that the ones in the Lidl set won't be the size that you need.

However it's a handy box for adding the extras you later purchase.

Theo (who still bought one of those sets anyway)

Yes, OP here, that's how it seemed to me, just pipe dimensions and tolerances but nothing about sealing O-rings.