View Full Version : Tips for a successful *Union* connection

06-07-2012, 08:05 PM
Do ya'll always Dope the face on either side of a union prior to installing.
Or just when it it just won't seal tight do you dope it.

Planning to make 2 union connections this weekend.....and want to get it right on the 1st shot..as it's a tight spot I'm working with.

06-08-2012, 07:26 AM
Every time on the side with the "nut" and also on the back of it where the nut turns against the union half. If it doesn't "seal tight", you use bigger wrenches, not more dope.

06-08-2012, 08:59 AM
Picked up the unions at the local shop.
Did not like the castings on thems.......

Went to the local orange. Watts branded PRC unions...much smoother faces.

I know unions need cheater pipes...to snug'em tight. I'd just like to treat it as worst case scenario.....as it's a tight spot I'm working with and I'd hate to mess it once the 1st snug up - leak test is done.

06-19-2012, 01:26 PM

Really? Just bigger wrenches? I have tried that but have already distorted two unions. I didn't use dope though. Has to be a torque spec/limit somewhere.

I'm also having trouble getting them to stop leaking.


06-19-2012, 03:15 PM
Hey Chris....unions do like to be nice and tight.
I avoid them ...unless I really need to have one in a fitting.

Remove them. Check the mating surfaces. see if the castings are clean.
The ones from Home Burrito were much cleaner than the ones I picked up from the supply shop

Tom Sawyer
06-19-2012, 03:15 PM
I don't use dope and I don't need big wrenches either. Make sure they align correctly.

Gary Swart
06-19-2012, 03:44 PM
In day of yore when I was just a kid on the farm, galvanized pipe was all there was. My dad taught me to put a union in every so often so the line could be disassembled without cutting and/or backing off a dozen joints. As I recall, we used no dope except on the union to pipe connections, and our largest wrenches were 18" and 24". ( I still have them although they get little use anymore) We never used a cheater except to remove a stubborn 2" joint. All we did was to make sure we had a good alignment of the joint. I do not recall ever having a leak.

06-19-2012, 06:18 PM
As noted, if the pipes don't line up straight, a union can have trouble sealing. A little pipe dope doesn't hurt, but it isn't necessary, and can help. What can be more of a pain is taking a good joint apart, then fixing something, then putting it back together. Then alignment is even more critical as the first time it likely deformed the sealing surfaces - get it off just a little, and it can take a lot of force to make a new seal.