Compression slip coupling and plastic insert

2 Feb 2013
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United Kingdom
I bought this compression slip coupling recently:

to fit to a plastic pipe at one end and a copper pipe at the other.

I put in a superseal pipe insert in the plastic pipe - this one:

However, the insert didn't fit in the coupling at all.

I didn't have the other insert to try:
but would this have fitted?
Otherwise how do you connect this coupler to a plastic pipe?

And now to your opinion.
There was a T soldered connection under the floorboard leaking. The top of the T was no longer in use and capped, so only 22mm and 15mm pipes on either side carrying water.
What's the best way to fix the leak?

I used a speedfit reducer then plastic pipe to make up the length then the slip coupling above which didn't work. I chose the slip coupler because I didn't know if the pipes would have enough room to move about for a normal coupler.

Since the plastic insert didn't fit the compression slip coupling and the pipes could move, I used an equal speedfit coupler and was more than happy with it in the end.

I realised afterwards I could have replaced the plastic pipe with a copper one to fit the compression fitting but I first thought of using a plastic pipe so I could bent it slightly out of shape to put a normal coupler in place before deciding to go for the compression slip coupling.

I'm glad I didn't use the compression fitting in the end. There's always a risk of over or under-tightening it and create a small unnoticed leak under the floorboard. Plus it was very awkward bending down to handle 2 spanners under the floor boards. I still have marks on my body today to show for it. Fitting the speedfit coupler was a breeze.

So how would you have fixed the leak - what fittings would you have used? The pipe was not part of central heating.
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Of the items linked to, the fitting is 22mm, the inserts are 28mm and 15mm, so no combination of them would fit together.
With the correct sizes, the insert without rubber seals is used with compression fittings.
The insert with rubber seal is only for use with the matching pushfit fittings.
Wrong links! Just assume all sizes are correct.
I guess when using compressing fittings with plastic pipes, the inserts aren't supposed to provide a watertight seal, the olive does that.
Didn't think about that.
Is it the case then for all compression fittings - superseal inserts won't fit them?
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The outside diameters of plastic pipe are standardised - i.e 15mm, 22mm or whatever.
The inner diameters may not be so its best to use the insert that's recommended for that make of pipe. The insert prevents the pipe from collapsing.
When you push the pipe into your slip coupling, ensure that the copper olive compresses down onto the pipe insert, so don't push it in too far.
John :)

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