Hydronic NPT Fitting Tightening - Proper technique

rossn

I have a remodel, where I am installing a lot of uponor stainless manifolds and other various distribution fittings. I want to make sure I am getting it right, and could use some guidance on how tight to tighten various NPT fittings. Most are brass, and the manifolds are stainless. Most are 1/2"-1", though there are some 1-1/4" Tru-Flow brass manifold elbows with a rubber gasket (A2620090) and they mention using silicone.

I'm planning on using 1/2" Blue Monster PTFE tape and Hercules Megaloc. A well known old timer in this area told me to go paste, 3-5 wraps tape, paste.

My question is how tight to go on the various fittings, since I am not a tradesman. Are there some general guidelines for knowing how tight to go? I think I've also seen wrench sizes referenced.

Thanks so much for your help!

ChrisJ

I was taught 1 foot of wrench per inch of pipe.  So 12" wrench for 1" pipe.

To be fair I use 14" on 1".

For tightening you need to go by feel but it also depends on the material.  I feel for a bind feeling,  meaning you'll feel it get tighter and tighter but it's fairly linear.  When it gets a lot tighter all at once is when you're in the area.

mel57

As Chris said, you need to go by feel. I was taught,  that the pipe threads should go as deep into the fitting ,that it has threads. Usually, you'll have 2 threads left showing. Keep in mind that each fitting, and pipe thread, probably didn't come out of the same machine.  So they'll behave a little differently. 

mattmia2

It has a lot to do with where you need it to point. It will seal at a wide range of actual torques/tensions. you stop when it is aligned where you need it and you feel that it wouldn't make it another turn without a lot of effort. too much tape can gum things up too, especially with a thicker tape like blue monster i wouldn't go more than 2-3 wraps. Lots of factory fitting and nipple threads are very poor. it seems especially on brass for some reason.

JohnNY

So, to be clear, you're not sure or comfortable assembling fittings but you're installing radiant heating? Is that going to work?

ChrisJ

JohnNY said:

So, to be clear, you're not sure or comfortable assembling fittings but you're installing radiant heating? Is that going to work?

I'm sure you had a first NPT joint, no?
If you gave up and never started what would have happened?

mattmia2

I made up a lot of NPT fittings that didn't leak before I thought i was probably doing it right. There is a torque suggestion out there for the different threads. Number of threads engaged is also a measure, but thread quality is generally poor so neither is very accurate.

hot_rod

The fitting you show is a BSP straight thread, it should not use any sealers, wet the fiber gasket first, the O-ring on the other side of the ell makes the other seal.

We assemble BSP straight pipe threads with Loctite 272 , if it is not a gasketed connection.

For NPT threads Blue Monster 3 wrap, maybe a bit of pipe dope.
For stainless NPT threads, use a stainless specific tape and pipe dope.

Many folks over tighten pipe threads, use a 12- 14" wrench for pipe up to 1" to avoid over tightening. Teflon really makes it easy to go too tight

ratio

& the old 'bury the threads & a turn for luck" doesn't always work, although it did make it easy to find the old brass fitting someone had put on a gas line I came across some time ago.

mattmia2

@hot_rod I didn't look at the link. I was answering for NPT. A gasketed fitting is tightened by hand until the gasket touches then a little more to compress the gasket and hold it in place, maybe 1/4-3/4 turn or so depending on the gasket material and fitting material.

JohnNY

ChrisJ said:

JohnNY said:

So, to be clear, you're not sure or comfortable assembling fittings but you're installing radiant heating? Is that going to work?

I'm sure you had a first NPT joint, no?
If you gave up and never started what would have happened?

My first installation wasn't radiant heating manifolds, and I was supervised by my father and brother, both licensed plumbers.

JUGHNE

I piped 2 HTP Phoenix WH's with recirc and temp valves all in SS.
Fittings, unions and factory nipples. Less money than LL brass or copper (considering many unions and male adaptors).
No Galv allowed on these WH's.

The only problem was getting some unions to seal. SS is harder than brass. Needs more wrenching to seal.
Very easy to crack female brass fittings by comparison.

ethicalpaul

If everyone on this forum had a father and brother who were licensed plumbers I guess there'd be a lot fewer posts, at least about plumbing stuff!

GroundUp

NPT fittings are designed to have a 1/2" make-in on everything under 2" nominal. So a 1" nipple should screw into a fitting only 1/2" and be the proper amount of tight. Sometimes that still feels loose, and sometimes it's tough to get them in that far but that's what they're "supposed" to do. Personally I feel the "foot of wrench per inch of diameter" idea only works for certain sizes. A 12" wrench is too small for 1" and a 24" is too big for 2" IMO. It's tough to say what's tight because everyone has a different feel for things- personally I use 18" wrenches for everything from 3/4" to 2" and each one has a certain amount of resistance in relation to the make-in.

ChrisJ

GroundUp said:

NPT fittings are designed to have a 1/2" make-in on everything under 2" nominal. So a 1" nipple should screw into a fitting only 1/2" and be the proper amount of tight. Sometimes that still feels loose, and sometimes it's tough to get them in that far but that's what they're "supposed" to do. Personally I feel the "foot of wrench per inch of diameter" idea only works for certain sizes. A 12" wrench is too small for 1" and a 24" is too big for 2" IMO. It's tough to say what's tight because everyone has a different feel for things- personally I use 18" wrenches for everything from 3/4" to 2" and each one has a certain amount of resistance in relation to the make-in.

I just did a lot of 1" and I used a 14" for tightening and an 18" to hold.

Personally I think the 14 is nice for 3/4 and 1".  

These are from Ridgid on the subject.

mattmia2

Maintaining a gap tends to crush the pipe especially if it is seized.

hot_rod

1 grunt for 1/2- 1", two grunts for 1-1/4- 2" pipe.

ChrisJ

mattmia2 said:

Maintaining a gap tends to crush the pipe especially if it is seized.

I've had a similar discussion with a good friend over the subject who makes the same claims. I always leave a gap my self, and, the original patent from Stillson suggests the same.

https://patents.google.com/patent/US95744A/en

https://patentimages.storage.googleapis.com/24/33/55/3fa81a64ad8681/US95744.pdf

rossn

Hi all, great discussion, and thanks for all the information from everyone! Greatly appreciated, and some very good information to go on. Sometimes you think you have been doing things OK, but it is good to get confirmation before going on to something bigger.

Before getting back to this thread, I talked to Uponor on that Elbow, and @mattmia2, you nailed it - slightly snug by hand + ~1/4-1/2 turn. Thanks! Now, their instructions mention silicone oil on the male threads... does anyone know if using silicone paste, like the oatley, an OK substitute? I'm assuming it is just to allow for consistent, even torquing.

On the wrench size, lots of good information here. Everything I will be tightening should have flats (fittings... propex for the rest). I'm assuming rough wrench sizes still apply to crescent wrenches, though knowing the right tightness is still a bit of a learned skill. I suspect even amongst tradesmen there is a bit of a variance, given the individual. @chrisj - loved your description of the torque relative to tightness... that was meaningful.

I don't know what to say JohnNY. Some are more timid to learn on their own than others who are more confident. If I was that type, I probably wouldn't do my own brakes on my car, taught myself rock or ice climbing, or do something like a remodel and it's design work. Sometimes the guy who hasn't done it before but doesn't mind taking the time and care can do better than some of the people they would hire, though there are plenty of folks out there doing great work.

Let's be real here, we're talking low pressure water... there isn't going to be some catastrophic failure, such as with a pressure vessel, or a gas explosion, and if the pressure test holds fine, it is likely fine.

Again, thanks everyone!!! This is a great group of folks... I'm sure I'll be back for some more guidance!

hot_rod

I use a small dab of chapstick on O-rings, faucet stems, even copper to brass compression ferrules on supply tubes and valves.
It's basically beeswax, mineral oil and maybe some fragrance.
If it is safe on your lips....
It certainly travels well in toolboxes and pockets Works well on lips and cracked fingers in the winter.