Tips / Tricks for getting threaded pipe to seal? - Page 2

AC_Hacker · 01-12-17, 11:02 PM

Daox,

I had a similar problem with a heat pump project.

Standard pipe thread is tapered and relies on a progressive interference fit to work.

There are other pipe thread systems that do not rely on tapered, progressive interference to work. Instead, they use a flat compression washer. The straight threads supply force to compress the washer.

If you were crossing systems, it would feel gritty, because very small bits of thread faces were being sheared off by your struggle to make it seal.

One give-away is that the thread shoulder (male and female) has a precision-machined surface.

There's a good chance that the damage to the threads is not completely fatal yet. If the machined surface of the shoulder is still intact and undamaged, you may be able be successful.

Of course, you need the proper straight-thread part and the proper compression washer.

If the damage has been too severe, there's epoxy.

Best,

-AC_Hacker

Daox · 01-13-17, 09:29 AM

Thanks for the tip AC Hacker. I'm aware of this. The unit we were working on had male NPT threads on the outside. They were definitely tapered.

AC_Hacker · 01-13-17, 11:30 AM

When you said that "half the joints leaked", what are you referring to? Your heater only has two, IN an OUT, right?

Are they leaking?

Are half of all the joints you put together leaking?

This is very strange.

It sounds like you have been invaded by a different Physics that doesn't apply in the rest of the universe..

Maybe you should go copper at the heater, and switch to PEX ASAP.

-AC

gasstingy · 01-13-17, 01:30 PM

Gasoila is used in the gas station business for installing underground tank fittings and more. You could likely find a petroleum equipment supplier (relatively) locally that would have it.

Hope this helps

Daox · 01-13-17, 01:53 PM

We made a few other connections off the heater to ball valves for flushing the heater with vinegar.

In the end, we switched from the threaded fittings to compression fittings as that was another option that came with the heater. Those sealed up just fine.

oil pan 4 · 01-13-17, 03:08 PM

To get 3/4npt fittings to properly seal it takes 100ft.lb, I have found that most npt fittings that leak are not any where near tight enough.

1234enough · 01-24-17, 03:58 PM

I use Loctite 55, its a cord with PTFE or the like on the cord, seems to keep on the thread better than PTFE tape and you can realy feel it's there when tightening up the joint.

rclark762 · 02-06-17, 04:23 AM

Quote:

Originally Posted by stevehull

Daox,

Don't feel bad . . . .

Teflon pipe tape works great if the threads are in good shape. More recently, the quality of metal pipe threading has gone to hell.

I never had leaks, in the past, but I get them regularly now if I just use teflon tape.

I still use teflon tape on the outside threads, but now always use pipe "dope" on the inside threads. A bit more time, but NO leaks.

Hope this helps.

Steve

ps pipe dope is messy and nasty . . .

+1 to this comment.

creeky · 02-25-17, 11:09 AM

Quote:

Originally Posted by oil pan 4

To get 3/4npt fittings to properly seal it takes 100ft.lb, I have found that most npt fittings that leak are not any where near tight enough.

When I fitted propane into my camp I could not believe how hard I had to lock those fittings down. And that was with pipe goop. Basically it took every ounce of muscle I had and then going back the next day and doing it again.

Thx steve for the idea to wrap the inner threads and goop the outer. I will try that next time.

01-12-17, 11:02 PM	#11
AC_Hacker Supreme EcoRenovator Join Date: Mar 2009 Location: Portland, OR Posts: 4,004 Thanks: 303 Thanked 724 Times in 534 Posts	Non-Tapered Threads Daox, I had a similar problem with a heat pump project. Standard pipe thread is tapered and relies on a progressive interference fit to work. There are other pipe thread systems that do not rely on tapered, progressive interference to work. Instead, they use a flat compression washer. The straight threads supply force to compress the washer. If you were crossing systems, it would feel gritty, because very small bits of thread faces were being sheared off by your struggle to make it seal. One give-away is that the thread shoulder (male and female) has a precision-machined surface. There's a good chance that the damage to the threads is not completely fatal yet. If the machined surface of the shoulder is still intact and undamaged, you may be able be successful. Of course, you need the proper straight-thread part and the proper compression washer. If the damage has been too severe, there's epoxy. Best, -AC_Hacker Attached Thumbnails __________________ I'm not an HVAC technician. In fact, I'm barely even a hacker...

01-13-17, 09:29 AM	#12
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	Thanks for the tip AC Hacker. I'm aware of this. The unit we were working on had male NPT threads on the outside. They were definitely tapered. __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

01-13-17, 11:30 AM	#13
AC_Hacker Supreme EcoRenovator Join Date: Mar 2009 Location: Portland, OR Posts: 4,004 Thanks: 303 Thanked 724 Times in 534 Posts	When you said that "half the joints leaked", what are you referring to? Your heater only has two, IN an OUT, right? Are they leaking? Are half of all the joints you put together leaking? This is very strange. It sounds like you have been invaded by a different Physics that doesn't apply in the rest of the universe.. Maybe you should go copper at the heater, and switch to PEX ASAP. -AC __________________ I'm not an HVAC technician. In fact, I'm barely even a hacker...

01-13-17, 01:30 PM	#14
gasstingy Journeyman EcoRenovator Join Date: Feb 2010 Location: Arab, AL Posts: 491 Thanks: 109 Thanked 49 Times in 43 Posts	Gasoila is used in the gas station business for installing underground tank fittings and more. You could likely find a petroleum equipment supplier (relatively) locally that would have it. Hope this helps Last edited by Daox; 01-13-17 at 02:15 PM..

01-13-17, 01:53 PM	#15
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	We made a few other connections off the heater to ball valves for flushing the heater with vinegar. In the end, we switched from the threaded fittings to compression fittings as that was another option that came with the heater. Those sealed up just fine. __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

01-13-17, 03:08 PM	#16
oil pan 4 Land owner Join Date: Nov 2012 Location: NM Posts: 1,026 Thanks: 12 Thanked 127 Times in 107 Posts	To get 3/4npt fittings to properly seal it takes 100ft.lb, I have found that most npt fittings that leak are not any where near tight enough.

01-24-17, 03:58 PM	#17
1234enough Lurking Renovator Join Date: Jan 2017 Location: uk Posts: 3 Thanks: 0 Thanked 1 Time in 1 Post	I use Loctite 55, its a cord with PTFE or the like on the cord, seems to keep on the thread better than PTFE tape and you can realy feel it's there when tightening up the joint.