Tips / Tricks for getting threaded pipe to seal?

Daox · 10-26-16, 10:28 AM

I was helping out my father in law install an on demand water heater last night. The heater has 1/2" threaded pipe fittings coming out of it. So, we ran to the store and grabbed all the stuff we needed (valves, fittings, etc) and came back and installed it. We pressurized it and had a few leaks. So we removed it, tightened them up as much as we thought safe and reinstalled it. Still leaking. We used teflon tape on every joint and I'd say nearly half of them leaked. This seems ridiculous.

So, what tips do you guys have for getting threaded pipe connections not to leak?

stevehull · 10-26-16, 11:34 AM

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 . . .

sunspot · 10-26-16, 01:02 PM

What stevehull said. I don't rely on teflon tape anymore unless it's a tiny (ie 1/8" NPT or smaller) fitting.

Daox · 10-26-16, 10:41 PM

Thanks guys, I'll have to give that a try next time.

randen · 10-26-16, 11:18 PM

For Really Really bad pipe threads I've resorted to 5 min epoxy.

Randen

stevehull · 10-27-16, 06:27 AM

Randen - I have also used silicone based caulk (the kind that cures to rubber). Will keep your suggestion of 5 minute epoxy in mind also.

I guess we have all found that threading has gotten rather bad . . . .

Steve

Daox · 10-27-16, 09:11 AM

Yeah, I did notice that while threading the pieces together it was not a nice smooth process. The joints felt 'gritty' for lack of a better word and didn't engage nice and smoothly.

oil pan 4 · 01-11-17, 02:24 PM

Use hydraulic fracturing rated pipe dope. Since fracking uses preasures in excess of 9,000psi at the well head and something like 13,000 or 14,000psi at total deapth you know it will work.
I used it on my 7hp gasoline pressure washer which runs some where between 2,000 and 2,500psi on its pipe thread connections since 2008 and I don't think any have ever leaked. The only ones that leaked were the ones I used Teflon tape on.

Daox · 01-12-17, 10:34 AM

Where do you get said pipe dope?

oil pan 4 · 01-12-17, 01:57 PM

Lowes used to have it.
After I posted this I went there to get some lumber and figured I would check to see if they still have it and they do not.
It was "gasoila" rated for -100°F to +600°F and10,000psi.

But I think any 10,000psi rated pipe dope would work just as well.

10-26-16, 10:28 AM	#1
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	Tips / Tricks for getting threaded pipe to seal? I was helping out my father in law install an on demand water heater last night. The heater has 1/2" threaded pipe fittings coming out of it. So, we ran to the store and grabbed all the stuff we needed (valves, fittings, etc) and came back and installed it. We pressurized it and had a few leaks. So we removed it, tightened them up as much as we thought safe and reinstalled it. Still leaking. We used teflon tape on every joint and I'd say nearly half of them leaked. This seems ridiculous. So, what tips do you guys have for getting threaded pipe connections not to leak? __________________ 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.

10-26-16, 11:34 AM	#2
stevehull Steve Hull Join Date: Dec 2012 Location: hilly, tree covered Arcadia, OK USA Posts: 826 Thanks: 241 Thanked 165 Times in 123 Posts	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 . . . __________________ consulting on geothermal heating/cooling & rational energy use since 1990

10-26-16, 10:41 PM	#4
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	Thanks guys, I'll have to give that a try next time. __________________ 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.

10-26-16, 11:18 PM	#5
randen Uber EcoRenovator Join Date: Apr 2011 Location: Strathroy Ontario Canada Posts: 657 Thanks: 9 Thanked 191 Times in 129 Posts	For Really Really bad pipe threads I've resorted to 5 min epoxy. Randen Last edited by Daox; 01-13-17 at 02:16 PM..

10-27-16, 06:27 AM	#6
stevehull Steve Hull Join Date: Dec 2012 Location: hilly, tree covered Arcadia, OK USA Posts: 826 Thanks: 241 Thanked 165 Times in 123 Posts	Randen - I have also used silicone based caulk (the kind that cures to rubber). Will keep your suggestion of 5 minute epoxy in mind also. I guess we have all found that threading has gotten rather bad . . . . Steve __________________ consulting on geothermal heating/cooling & rational energy use since 1990 Last edited by stevehull; 10-27-16 at 07:40 AM.. Reason: speling errors

10-26-16, 01:02 PM	#3
sunspot Apprentice EcoRenovator Join Date: Apr 2012 Location: Vancouver Island, BC Posts: 147 Thanks: 30 Thanked 35 Times in 29 Posts	What stevehull said. I don't rely on teflon tape anymore unless it's a tiny (ie 1/8" NPT or smaller) fitting.

10-27-16, 09:11 AM	#7
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	Yeah, I did notice that while threading the pieces together it was not a nice smooth process. The joints felt 'gritty' for lack of a better word and didn't engage nice and smoothly. __________________ 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.

01-11-17, 02:24 PM	#8
oil pan 4 Land owner Join Date: Nov 2012 Location: NM Posts: 1,026 Thanks: 12 Thanked 127 Times in 107 Posts	Use hydraulic fracturing rated pipe dope. Since fracking uses preasures in excess of 9,000psi at the well head and something like 13,000 or 14,000psi at total deapth you know it will work. I used it on my 7hp gasoline pressure washer which runs some where between 2,000 and 2,500psi on its pipe thread connections since 2008 and I don't think any have ever leaked. The only ones that leaked were the ones I used Teflon tape on.

01-12-17, 10:34 AM	#9
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	Where do you get said pipe dope? __________________ 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.

01-12-17, 01:57 PM	#10
oil pan 4 Land owner Join Date: Nov 2012 Location: NM Posts: 1,026 Thanks: 12 Thanked 127 Times in 107 Posts	Lowes used to have it. After I posted this I went there to get some lumber and figured I would check to see if they still have it and they do not. It was "gasoila" rated for -100°F to +600°F and10,000psi. But I think any 10,000psi rated pipe dope would work just as well.