working with black iron pipe

[ssupercoolss]

when i finally get my boiler in place, i will most likely be doing most of the piping with black iron. i have done quite a bit of work with BO pipe, have access to pipe cutter and threader, etc.....but is there some magic number you assume on how much pipe actually threads into a coupler or elbow? example - if i need this elbow here, and another elbow over there, and i measure in between the two, and come up with 25", what length should i actually cut the pipe at?

 

[Couderay80]

What you need here is a pipefitting lesson. First and foremost start with good sharp threads. When you tighten the fitting you want 3-5 turns by hand. Pipe is to be clamped down in a pipe vise (tripod). Back off the fitting and get you some rector seal #5 coat the male threads with the dope and put a small dab on the fitting tighten up by hand (3-5 turns) then using a pipewrench tighten a couple more turns until tight. use a 18" wrench on 3/4"-1-1/4" size pipe. Now getting to your question. Pipe fittings usually take off there size minus an 1/8 of an inch with 150lb fittings, meaning a 1-1/2" 90 takes off 1-3/8". This also works on full size tees. 45's are different as are reducing tee's and 90's. Make up usually is 5/8" on most fittings meaning the male threads go into the fitting 5/8". sounds confusing it really isn't but I could tell you more if you need answers to other questions. E-mail me if needed.

 

[SnaykeByte]

What you need here is a pipefitting lesson. First and foremost start with good sharp threads. When you tighten the fitting you want 3-5 turns by hand. Pipe is to be clamped down in a pipe vise (tripod). Back off the fitting and get you some rector seal #5 coat the male threads with the dope and put a small dab on the fitting tighten up by hand (3-5 turns) then using a pipewrench tighten a couple more turns until tight. use a 18" wrench on 3/4"-1-1/4" size pipe. Now getting to your question. Pipe fittings usually take off there size minus an 1/8 of an inch with 150lb fittings, meaning a 1-1/2" 90 takes off 1-3/8". This also works on full size tees. 45's are different as are reducing tee's and 90's. Make up usually is 5/8" on most fittings meaning the male threads go into the fitting 5/8". sounds confusing it really isn't but I could tell you more if you need answers to other questions. E-mail me if needed.

PERFECT advice! Good post.

 

[Willman]

Good info, Thanks. My question on piping has been on the sealant that squeezes out into fitting or pipe. I take the time to clean it out, sometimes tying a rag to a rod for deep cleaning. Am I being too fussy ? I figure its not needed for sealing so why leave it. Doesn't take too long anyway.
Will

 

[Tony H]

With cleaning just remember anything in the pipe will be in your system, but I have never seen a plumber clean the dope off inside connections of installed pipe. However I have seen them clean out / off pipe that is being reused mostly by taking a wire brush to the threads so old dried dope does not cause a leak.

 

[steam man]

I wouldn't apply any pipe dope to the internal thread though I have seen it done. Apply it a thread or two from the end of the male fitting. Nothing should be getting into the system. That was on my license exam years ago. Dope or tape can be used up to 2". Over that just dope. I really like the dope-tape-dope trick. It just seems like it works every time. I like to see at least half the thread screwed into the fitting. 5/8" sounds about right. Just don't bottomthem out. It is an art to getting threaded connections to end up just right. Its nice to have some flexibility near the end connection. That's why I like welded up fittings. You just get an exact fit.

Mike

 

[Willman]

Thanks guys
Will

 

[Jersey Bill]

A plumber taught me to run the die until there are 2 threads out the other side.
On small diameter pipe this will get the end within 1/8" of the other pipe at a 90. So the length to cut is about 1/8-1/4" less than the inside length required.
I dont use tape on gas because small slivers can end up in the pipe which can jam up screens and orifices.

 

[Dave T]

I finished piping the EKO in my basement and did the pipe fitting like mentioned above in small sections then (coupled) the sections together, all the pipe joints to 90's and tee's were water tight no problems..I did have two leaks at brass shutoffs but I feline footed them because this was my first (big pipe) piping job and I was skeptical of the BRASS integrity,I am here to say two to three threads showing worked every time..That was the good news BUT the bad news was all but one coupling that I installed leaked, on my system thats 6 leaks I used pipe dope on the brass insert and redone the couplings and NO LEAKS is this bad practice and why..Dave

 

[in hot water]

Are you using couplings, or those "protectors" that come on lengths of pipe. Those fittings are not true couplings as they do not have a tapered thread inside. Look into one to see the thread just goes through. It's better to buy a banded or merchant coupling.

Also try some of the new "three wrap" teflon tape products. It is a much heavier gauge teflon tape and really does work with three wraps and no additional dope added.

In Europe the pipes are connected with no taper threads. They use hemp or Loctite cord to seal them. Most Euro boilers arrive with straight threads and often include this bag of hemp. No smoking allowed

The nice part of a straight thread for pipe fitting, once you get used to them, is you length is always exact, as you stop anytime not when the taper takes up.

hr

 

[Dave T]

The leaks that I had were not the thread to pipe they were the coupling to coupling threads and I was not shy about using 2 foot leverage bars on the pipe wrenches to draw them as tight as I could but they leaked untill I doped them up(MAYBE I AM USING THE WRONG DOPE HAND OVER THAT HEMP LOL) I have the piping sitting with almost 30 PSI in them now and no leaks..If the pipe dope gets on the inside of the pipe will that cause issues with anything??Dave