Bath trap slips off when turned for tightening

Jupiter01 · 22 Oct 2019

On my bath, I have one of these:

It's all fitted on okay. When I go to screw one of these on the bath waste:

The tightening of the nut goes so far and then it slips off. I then start again and the same thing happens. At first I thought that the fitting my not be straight or stretched by the waste pipe but even when I try it alone (disconnected from waste pipe), the same happens.

I am not trying to over tighten it either but as soon as it's ready for a couple of extra turns, it slips off. I am hoping this makes sense and you guys ca relate to this.

Thanks in advance.

ktuludays · 22 Oct 2019

Had this a lot with cheap fittings.

Always resolved with a good quality fitting such as mcalpine.

Jupiter01 · 22 Oct 2019

Both are Floplas in my case. Are they the "cheap fittings"?
Can I try this mcalpine trap instead? I'd rather not remove the waste again as its siliconed in:

How do I know if the issue is with this or the thread on the waste

terryplumb · 22 Oct 2019

Are you possibly cross threading ? Ensure the trap and waste are totally in alignment , before screwing together turn the nut anti clockwise a bit , helps to align the start of the threads.

footprints · 22 Oct 2019

terryplumb said:
Are you possibly cross threading ? Ensure the trap and waste are totally in alignment , before screwing together turn the nut anti clockwise a bit , helps to align the start of the threads.

Yes sometimes you can feel or hear a slight click as it passes the start of the thread then screw up.
Plastic threads are **** once crossed or over tightened best to change , another thing is the nut might have split so it opens up under pressure and slips out of the thread.

Jupiter01 · 22 Oct 2019

Thanks guys. The slight click rings a bell!
Will I get away with replacing the trap with a McAlpine fitting or will it be necessary to replace the bath waste too?

footprints · 22 Oct 2019

Try the mcAlpine if the bath end looks OK it tends to be the female thread that gets screwed as a rule!

ReJect · 22 Oct 2019

Try a different brand trap.
McAlpine trap worth using if you can source one.
I am a plumber and had same happening on an all new parts bath replacement job and I tried replacing just the bath waste but still had identical problem. When I tried a different brand trap it was a nice tight fit on the bath waste threads. Strange thing was the first trap I used was a standard good quality type.
Proves that threads vary - especially on plastic waste fittings.

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Bath trap slips off when turned for tightening

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