Compression fitting on plastic pipe

1 Dec 2007
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United Kingdom
Hello under the kitchen sink I have a compression fitting type valve that feeds the dishwasher hose.
This (the compression fitting) turns a little on the plastic pipe when I press the valve lever to isolate the hose but there is no leak.
Is this likely to cause an issue?

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You could maybe nip the fitting up a little but considering how often you use the tap I’d just keep an eye on things.
The fitting isn’t likely to blow apart!
I was hoping that at worst it would leak rather than blow off.
I'll keep an eye for it.
Is it possible that the plastic pipe itself is turning ? If the pipe goes into a plastic push fit fitting ,it will turn.
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Aren't these compression valves for copper pipe?

Does an olive seal properly on plastic pipe?
Compression fittings on plastic pipes are fine. The pipe needs a stiffener ( inserted into pipe) just as it would when using push fit fittings.
Mark a pencil line on the plastic pipe, right behind the compression nut. Mark another line at 90 degrees to the first line and make it in line with the tap lever. If you can see where the pipe is connected at the other end you can make similar markings.
Each time you use the tap to isolate the hose just check to see if the lines have moved.
If either of them has moved, then this is proof it is not secure. The end of the plastic pipe that the valve sits over should have an insert fitted, (as stated above). Does yours have this insert fitted?
As the outside diameter of the plastic pipe is the same as copper - in this case15mm - a brass compression coupling can be used.
It is essential to use an insert (preferably steel), the cut off pipe end needs to be square, and a copper olive is best, I find.
Ensure the pipe is pushed in as far as it will go!
Some fittings lend themselves better for this than others...... the two O ring JG Speedfit insert I find projects too far for radiator valves but the single one is OK.
John :)
Aren't these compression valves for copper pipe?

Does an olive seal properly on plastic pipe?
Compression fittings are fine on plastic pipe, always use an insert (stiffener), best to use a copper olive rather than brass and don’t use any jointing paste
I have decided to renew the section.
This was put together by a kitchen fitter, not a plumber.
I will replace the plastic pipe with copper.
My question is, can i leave the existing pushfit and just stick in a section of copper or is it dodgy to replace a lenght of pipe but using the same pushfit.

Just to clarify, the setup is t pushfit, plastic pipe and then compression valve.
You can if you wish ,but the copper pipe will turn in a push fit fitting ,just the same as a plastic pipe will. And for the cost of a new fitting it's hardly worth re using an old one.

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