Plastic pipe inerts

I too have been using plastic pipe with new inserts for some while and have noticed exactly the same thing. They are a real swine to get out of the fitting if pulled out of the pipe when breaking a joint. However, like you, I have had no leaks or any real problems - in fact as previous DIY user of compression and Yorkshire fittings I think the plastic version is "the dog's".

 

I thought the inserts were only for use with compression fittings, not push-fit. (If this is not the case I may have a lot of potential problems on past jobs!).

 

There are 2 different types of inserts. For compression they are plain and simply reinforce the pipe. For push fit, the insert has an additional sealing ring, (which won't generally allow a compression olive over it).

 

There are 2 different types of inserts. For
compression they are plain and simply reinforce the
pipe. For push fit, the insert has an additional
sealing ring, (which won't generally allow a
compression olive over it).

And boy did I struggle with those compression fittings until I discovered that the copper inserts are best for that (although still make for a very tight fit).

 

There you go. For some reason Screwfix only offers the inserts with the sealing ring suitable for push fit. The other inserts do look exactly like the copper inserts you mention but they shouldn't be that tight. Try a plumber merchant for the genuine speedfit compression insert. I'm told that the preference is for copper olives with the plastic pipe rather than brass, probably softer.
I agree with our other contributors - the inserts do pull straight out of the fitting if you try to disassemble - a real pain!