How to repair/seal stripped plastic thread?

[essayer]

Looks like the thread on our swimming pool pump’s drain have been stripped

The pump has a plastic body and the bolt seems sound, but it won’t tighten and can just pull out

How can I fix? I don’t care if the bolt stays in permanently, as I can drain from the top

[Murph7355]

How big is it?

Is the thread gone, or just full of gunk?

Have you tried wrapping judicious amounts of PTFE tape around the bolt and then given it a go?

I think you can also get some sealant called Plumbers Mate that might also be worth a go.

[shtu]

Couple more pictures would be handy, to see the body of the pump.

Is it a blind hole, or a flange? Could you drill right through and use long bolts to hole it all together?

If it's a blind hole, I'd consider a rivnut in there.

[essayer]

I think it’s roughly M12 size

It doesn’t seem to be full of gunk, I turn it to almost right, then it goes loose, plus I can just pull it out without much resistance
I reckon it was bodge sealed before we moved in last year

[shtu]

essayer said:

I think it’s roughly M12 size

It doesn’t seem to be full of gunk, I turn it to almost right, then it goes loose, plus I can just pull it out without much resistance
I reckon it was bodge sealed before we moved in last year

Bodgetastic temp fix

- cut a small piece from a coke can. Enough to cover half the circumference of the thread.
- place cut section into hole.
- tighten bolt.


There's 101 options depending on what you have to work with.

[pquinn]

If I was using what I had to hand I'd probably wipe a bit of PU sealant around on the thread (just a bit so it didn't push down into the pump on tightening) then tighten the bolt in.

[essayer]

Something like Fernox LS-X?

There is access on the inside from the pot but it’s curved on the inside



8/9 on here is the plug

[sassanach0]

just helicoil it.

[Turn7]

Murph7355 said:

How big is it?

Is the thread gone, or just full of gunk?

Have you tried wrapping judicious amounts of PTFE tape around the bolt and then given it a go?

I think you can also get some sealant called Plumbers Mate that might also be worth a go.

To much PTFE and the thread wont start, so it will go in pissed and then chew the thread up...likely the cause here.

Plastic threads and metal fittings are a total PITA at times.

[hellorent]

JB Weld

[Griffith4ever]

hellorent said:

JB Weld

For permanent - this!

JB Weld is incredible.

[sospan]

^^^^^^^^^^^^
A mate used JBWeld on a sump plug on a cheap runabout he had. He unscrewed the plug carefully during the setting time and it left a “new” thread. He did a lot more miles in that car.
As it’s your pump drain plug JB Weld an extension in there to connect to the external drain pipe effectively moving the joint outside the pump body.

[essayer]

You know what I just PTFEd the thread and it sealed up fine

Only to reveal a crack in the pressurised section, somewhere else.. probably requiring a new multiport valve. I’ll try JB weld on that..