Best thread sealant for the suction side?

[Jeff Lebowski]

I just cut an old and leaking threaded fitting off of the intake side of my pump and replaced it with a pump union. I used a bit of thread tape on the threads. There was some old residual sticky sealant in the pump housings female threads.

Unfortunately, my fix was no-fix and I now have a significant amount of air entering the pump basket. Using the hose trick, I think (and hope) that the leak is actually the union's threads where they enter the pump housing. My assumption is that I need to unscrew the union and apply some type of sealant to those threads.

Yes or No?

If yes, what type of sealant is best for this application?
If no, which mallet shall I use to smash this thing all to bits and then whack my forehead with?

 

[Texas Splash]

Pipe dope/sealant is very popular, along with a couple other items. Check out this discussion: Teflon tape or pipe thread sealant?.

 

[Texas Splash]

If no, which mallet shall I use to smash this thing all to bits and then whack my forehead with?

Of course if those don't work .....

 

[Jimrahbe]

Jeff,

Did you actually use a pump union, which has an O-ring to make the seal or did you use a union that you can buy at home depot?

If you put too much tape on a pump union, you might have made it so that the O-Ring never seats again the pump body..

Thanks,

Jim R.

 

[Jeff Lebowski]

I bought a pool pump union, not from HD but from a pool equipment supplier and I used thread tape. Probably two full turns, perhaps three on the threads. I may not have it tight enough, although it seemed pretty tight. I suppose it's possible that I did use too much and the O ring is not seating properly.

 

[Texas Splash]

I may not have it tight enough, although it seemed pretty tight.

Careful with those unions. Too tight is not good either as it can crimp the O-ring I believe. So once you re-tape, perhaps start fairly snug and tighten slowly from there?

 

[cfherrman]

Pull the union and remove the tape, the threads are just for moving the unions together.

Get silicon lube and lube the o ring and the threads and behind the union where the wing presses against. You just need the lube for anti seize on the threads and wing, sealer for the o ring.

Teflon tape imo is the best thread sealant, but for thread sealed connections. (Npt)

 

[Jeff Lebowski]

Just to clarify, I put Teflon tape on the threads where the union meets the pump. Not the threads on the other end of the union. I put nothing on those.

SO, you say use "silicone lube" for an anti-seize. Just regular aerosol silicone spray or silicone sealant?

 

[Txjole]

Vaseline on the o-ring and a dab on the union threads. Dope on the wet threads of the union.

 

[Texas Splash]

Vaseline

Probably meant pool silicone. Vaseline (petrolem-based products) can damage pool rubber o-rings.

 

[Txjole]

Union o-rings are generally Buna N now a days so Vaseline is OK. But yes I should not presume the current common standard. Silicone grease is best.

 

[cfherrman]

So no Teflon on the union? Good. Just keep the threads nice and clean and a small bit where I said for lube. You do not want a false torque so it's under tightened. Most likely hand tight and just a "click" with a wrench should do it

 

[Txjole]

 

[Jeff Lebowski]

Today I pulled the union and tried to clean most of the junk from the threads. Both the old "sealant" (I have no idea what was in there) and the thread tape which I applied last week. I then put some silicone goop on the threads and put the whole mess back together.

Waaaahhhhhhhh-laaahhhhhhhhhh. The offending Air-B-Gone. I still, however, have air at the pool water outlets, courtesy of leaks somewhere up on the roof-mounted solar heat panels. Arrrrrgh. Those bubbles make the pool vac levitate. This, of course, makes it worthless.

NEXT!

 

[sktn77a]

So you used one of these pump unions with silicone grease on the oring to seal the intake connection to the pump:

Pump Union 2

 

[Jeff Lebowski]

Yes.