how do I get my NPT connections to not leak

[ericm979]

How do you make NPT connections that don't leak? Too many of the ones I added recently leak. I have been using permatex liquid PTFE sealer.

 

[teg]

I'm wondering that too... I'm guessing that I tighten mine way too much... Anyone else?

 

[4570Man]

The only ones I’ve found that don’t leak I torqued the crap out of. If for some reason the rotation is limited it’s pretty much guaranteed to leak.

 

[KYErik]

It sounds counter intuitive, but it is possible to over tighten these fittings and distort the threads. Its better to tighten them just a little snug, then tighten just a little more at a time if they happen to leak.

 

[tomplum]

When you get those stubborn ones, use Permatex #1 Form a gasket in the tube.

 

[4570Man]

That’s opposite of my experience. Anything that’s not about as tight as you can get it with a regular wrench leaks.

 

[Oldpath05]

I thought this was Teflon Tape was for or am I on the wrong page again.

 

[/pine]

You can eliminate relying on thread sealant by switching to NPTF and using NPSM female fittings...all mechanical...stouter than JIC...!

 

[4570Man]

I’ve had better luck with the white liquid thread sealer. As in Teflon tape fails every time when oil is in the picture in my experience.

 

[downsizingnow48]

If it is hydraulic, I use Loctite 545. If it is water, I use Rectorseal #5. If it is gas, I use gas rated Teflon tape and sometimes Rectorseal as well. Never had any of these leak if the fitting is properly tightened.

The fitting could be too tight or too loose, it will leak either way. I always get them just about as tight as possible, but it is possible to over tighten. Also these days some fittings are poor quality and might not seal at all. I got some of those one time at a big box store.

 

[Billrog]

I've found you have far less chance of leaks if you allow the sealer to set over night before putting them into action. Some sealers work regardless but many don't.

 

[Dftodd]

Using permatex pipe dope is fine. There are two types. The types with chunks, and the smooth. The stuff with chunks is junk and doesn't dry. With the smooth stuff. Make sure the threads are clean and dry. Any oil or water, and it won't seal. I use break cleaner to clean the threads.

I've found that if I let the permatex dry up some, it seals better. I coat my threads, let them sit for a half hour or so to partially dry out. Then install. You want it mushy but not really sticky if that makes sense

 

[s219]

For hydraulic fittings that are steel or stainless steel, generally I get them as tight as I can muster. They normally won't deform up to that point. So snug the crap out of them. Regular plumbing fittings that are plastic or brass are a lot more fragile and those I am far more gentle with.

 

[Tractor Seabee]

Proper NPT hydraulic fittings are made of forged steel. Using normal length wrenches for the fitting there is no way you can over tighten. First thing happens is the corners of the wrench flats will round off if using open end or adjustable wrenches. If possible always use 6 point wrenches. Flare nut wrenches in the heavy pattern are great around hoses and tubing. Things that cause your leaks are: not tight enough, wrong lubricant/sealer used, damaged threads. SS or Forged steel on both male and female sides will not stretch unless you use a cheater bar. Over-tightening brass and malleable iron will stretch, cast iron will split, and internal threads in cast iron will strip out.

I very seldom have a leak in anything unless the threads are damaged or mating surfaces damaged or dirty; after many thousands of joints (not weed).

Ron

 

[bigdeano]

If the threads are clean and dry I use Locktite 242 blue thread locker. If oily I use Teflon tape. I tried the liquid Teflon products many years ago but couldn't make them seal because they don't harden. They just pushed out at high pressure. Never tried them again. I rarely have anything leak.

 

[David_Kb7uns]

Do not remember the name but the hydraulic hose place here sells a teflon sealer similar to Rector seal but has a quicker drying solvent and have never had a problem with it leaking.

David

 

[pmsmechanic]

You guys are working way to hard! Use a good quality teflon tape wrapped around the threads so that the tape gets tightened up as it goes in. I use 2.5 - 3 wraps. Tighten moderately tight and no leaks. If the flats on the fitting are starting to round off as you are wrenching you are plenty tight. I can't remember having a hydraulic leak on pipe fittings.

I know the code around here for natural gas is one time use only. They found there were too many leaks if pipe fittings were reused.

 

[Tractor Seabee]

I know the code around here for natural gas is one time use only. They found there were too many leaks if pipe fittings were reused.

That's because NG installs use malleable black iron fittings. They stretch like crazy when over tightened. When I was a service tech/installer in the industrial mechanical world we never re-used CI, brass, or malleable fittings for that reason. When someone is paying the bill you cannot afford call backs you can't get paid for. Fixing a bad install can take 3 times the labor.

Ron

 

[dragoneggs]

You guys are working way to hard! Use a good quality teflon tape wrapped around the threads so that the tape gets tightened up as it goes in. I use 2.5 - 3 wraps. Tighten moderately tight and no leaks. If the flats on the fitting are starting to round off as you are wrenching you are plenty tight. I can't remember having a hydraulic leak on pipe fittings.

I know the code around here for natural gas is one time use only. They found there were too many leaks if pipe fittings were reused.

Agreed. I like the heavier yellow teflon (for fuels/gas).

 

[mcfarmall]

Loctite PST 545 or 547 if I remember correctly, pipe sealant that comes in a tube.