Union threads -- Plasto Joint Stik or Silicon lube or both?


Sep 1, 2013
Trying to figure out how to achieve leak-free union joints. I'm installing them on both side of the pump so that it can be easily removed if necessary. I've seen one You Tube video where the guy put Plasto Joint Stik on the threads going into the pump body (seems reasonable since this is basically permanent). But for the union fitting is it best to use Silicon lube (so it could be eventually undone)? And lube up the o-rings, too?


Thanks again,


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Apr 1, 2007
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Re: Union threads -- Plasto Joint Stik or Silicon lube or bo

The threads have very little to do with waterproofing a union.....it's the o-ring that makes the seal....the threads simply compress the o-ring so the two flat surfaces mate properly.

You could certainly use lubricant on the threads if you wanted to but plastic doesn't corrode and, of those I have taken apart, a strap wrench is all I have needed.

I don't know what plasto joint stick is but I would not consider the threads into the pump as permanent......I would suggest you use pipe dope.

There is no real reason to lube the o-ring, either. If the union is installed correctly, the compression of the o-ring will seal the joint.