Pipe threads won't seal for me anymore!

Old 02-16-07, 11:04 AM
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Angry Pipe threads won't seal for me anymore!

Back when I was living in my mom's house, I was her "handy-girl". I never had a problem getting threaded pipe connections to seal.

Now that I'm an adult and finally a home owner (well - mortgage holder) myself, I'm also my own weekend plumber, but for the life of me I cannot get threaded pipe connections to not leak.

I've tried thread tape, I've tried pipe dope, I've tried silicone caulk, I've tried various nasty compounds from the home store (including one $20 jar of blue stuff), and 9 out of 10 fittings still refuse to seal and it seems there's nothing I can do to stop it.

Is it me? Or has the quality of threaded fittings gone down the pipes (pun intended) during the past few years when I was renting? I've noticed that the very few threaded connections that have sealed did so on the first try and have all had nice, sharp threads on the male fitting. Unfortunately all the threaded connections in the stores have rounded, dull male threads or, worse, a small channel running along the very tip of the thread as though the threading die was too dull and bashed the metal into shape (leaving a double ridge and channel) instead of cutting a nice, sharp thread. I think these rounded threads leave a gap for water to flow along, spiraling up in the threads and out my pipe connections.

Are the dull, rounded threads my problem? If so, is there a way to re-cut the threads to make them fit properly? I can't seem to be able to buy sharp, clean fittings any more. Or is there a different cause for the leaks.

Someone please help me! I want to be confident in my plumbing connections again.
Old 02-16-07, 11:39 AM
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The threads aren't as good. For non-gas threaded pipe, I use lots of pink tape from right after the first thread - like 5 layers of it. Then dope that. No leaks and the joints can be twisted later if you discover something doesn't quite line up.
Old 02-16-07, 02:20 PM
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So if the threads on fittings for sale today aren't nearly as good as they used to be (that's outsourcing for you), is it possible to buy a thread cutting die and tap to re-cut them or otherwise sharpen them up?

Or would re-cutting the threads just mess up the fittings more than ever?

I don't like the idea of just slathering on ever increasing amounts of tape and pipe dope. I've tried going down that path, though maybe not far enough, and I just don't know if I can trust the resulting connections.
Old 02-16-07, 02:34 PM
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If the thread dont look good. Yes Id take a die and chase the threads down. Also in boiler work They all ways told me make it tight as you can. Then another 1/2 turn on the pipe. Get a biger pipe wrench and a 3 ft piece of pipe that will fit over the handel of it . Bet they dont leak after that.

Old 02-16-07, 04:03 PM
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Funny seeing this "thread" today!

Spent the day at work on top of an airhandler above a large steam boiler trying to get a 2" union to seal.
All it took was what Ed suggested..........An 18" extension on a 24" pipe wrench.

The moral of this story is to use "more power".

It is possible that the quality of fittings has gone down but I view threads that are sharp on the edges as being a bad thing.
The edge of a fitting is not what seals it is the face of the thread that meshes with the opposing face that does it.
The only thing I ever got from fittings with sharp edges to the threads was cut hands.

Any piping manual will tell you that thread sealant of any type is only to lubricate the face of the threads to reduce the friction while the opposing surfaces of the threads were meshing into each other.
If you are applying an excess amount of sealant you may get a joint to seal sooner but there is the possibility that the joint could leak in the future.

I'm not saying it's impossible to get bad threads but if you pour on a bit more power it may help.

I'll add that a lot depends on what type of material you are working with.
Often when working with brass fittings you need to still apply a lot of force to the joint but if working with bad wrenches may wind up stripping the wrench flats before the joint is tight enough.
Experience really helps with these types of joints.

Last edited by GregH; 02-16-07 at 04:20 PM.

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