Leaks in Air Compressor Lines - Black Iron Pipe

[BIG JOE]

Hi Gang

I've nearly completed my stationary compressor system, and I go to fill it with air and am greeted with a hissing sound from (at least) two locations. Luckily, I added enough unions to allow me to tighten and such, but my first attempts at tightening have done little good.

1.) Should I not have pressurized the lines until allowing the pipe sealant to firm up overnight. (does it even firm up?)

2.) Should I not have bought the pipe at Home Depot? It's probably made in China, and a poster warned me about that.

3.) How much torque is necessary to seal the joints? I cranked pretty hard on most of the joints. Is it possible to overtighten?

Any suggestions would be helpful. I guess as a last resort I could have a buddy come by and weld the problem joints, but that seems extreme.

Cheers Joe

[John Crea]

Probably should have used teflon tape instead of thread compound

John

[Tom]

1) The sealant should not need to set overnight to work. 2) HD's black pipe is just fine. 3) Apply enough torque necessary to achieve a seal. Just gonna have to tear back to the failed joints, re-apply thread sealant, and maybe cap off just after to pressure check before piping any further. I feel your pain...Tom Joe wrote:>Hi Gang

Someday, it'll all be over....

[Doug Miller]

If you are depending on pipe dope to keep the joints from leaking, then you haven't made the joints tight enough.

Most stuff made in Communist China is crap. And even though it's pretty hard to screw up black pipe, you're still more likely to get pipe with the threads cut and tapered properly if you buy pipe that was made in a country with a capitalist economy.

Yes, it's possible to overtighten a joint so much that the fitting will crack. It takes a *lot* of force to tighten black pipe that much, though. Much more likely IMO that your joints are not tight enough, or that some of them are cross-threaded.

Squirt a little bit of liquid dish detergent or soap in a cup of water and stir it in well. Then use a paintbrush, or even your fingertip, to coat all of the joints with the soapy water. Pressurize the system, and you will see bubbles forming every place there's a leak. (BTW, this is the standard method of checking for gas leaks too.) Once you find out where the leaks are, you'll probably figure out why they're leaking too.

-- Doug Miller (alphageek at milmac dot com)

How come we choose from just two people to run for president and 50 for Miss America?

[Joe Nation]

I agree with Tom. The joints will have to be tightened until there is very little of the cut thread left exposed. If they are tightened enough the air leaks will stop - even the minute ones that cause the system to leak down over a period of several hours.

[Ralph Roseburg]

You should use rector seal #9 for the sealing compound, depending on the pipe (say up to 1") size you are using you should be able to tighten the threads 3 to 4 turns for a hand tight fit, if less than 3 turns your threads wont seal! if more than 4 to 5 turns the pipe will screw in too far and possibly bottom out and not seal depending on the type of fitting it is going into. You should use sharp pipe dies to cut the threads if they are not sharp the threads will not be sharp and true you must use an ample amount of cutting oil when cutting the threads. You should only use pipe couplings that are steel with a designated as taper tap/ most couplings sold in hardware stores have straight pipe threads and don't seal as easy and taper tap couplings

[Dave Mundt]

Smart move. Leaks are a continual problem, and, having some flexibility to get rid of them is a good thing.

I assume you mean pipe dope (the putty stuff?). It has been my experience that it should both stay flexible "forever" and if it is going to seal the pipe it should do it when the pipe is tightened up the first time.

I have seen some variation in connectors from the BORG. I doubt it is a problem with the pipe, as that seems ok. There is a decent chance that the fitting has been threaded too far, though.

Well, it is possible to overtighten, I suppose, although I have really only split a PVC fitting by overtightening. Metal pipe is pretty tough. I screw it in hand tight, then, crank another turn or so with a wrench.

Yea...that is "iffy". I would suggest, first off, swapping out the leaking fitting for a new one. Kind of a hassle, but, might be easiest in the long run. Alternatively, you could switch over to teflon tape.... Regards Dave Mundt

[James D Kountz]

I dont know is this is right or not but I used 2-3 wraps of teflon tape on my fittings and I only had one leak and that one was a nipple on my brad nailer. I either got really lucky or the tape works alot better than the goo. Something to think on.

Jim

[Anonymous]

-- I AM NOT PARANOID .. .. .. but EVERYONE thinks I am !! !! !!

[Greg]

I went with dope alone and the only leaks I have are at the quick disconnect couplers. (I chased them for a week or two) I did crank the pipe joints down to 1 1/2 - 2 threads showing per an old plumbing book I have. That took 24" pipe wrenches. I assembled as much as I could on the ground and made the last few joints in place with unions..

[Tim Carver]

Are you sure the system isn't leaking at your quick release fittings? These are the obvious leakers in any air system, and there is an enormous difference between good quick release fittings and cheap ones.

Tim Carver [e-mail]

[TomS]

Plumbers mix this gray powder with water and apply that to threads before screwing together. I don't know what max pressures it will support, but I fixed my black pipe garage compressed air system using this. I remember how disappointed I was after final joint was completed and hearing the hiss. But that was nothing compared to my amazement at how #$!%*@ up some of the cut threads were. I mean holes between threads. Until now, I never paid that kind of attention to threads. I kinda remember about $4 at any plumbing shop. Also, its organic, but don't breath it. Dries in about an hour, 24 for full cure; its only the water that needs to evaporate. Good luck, Tom.

[The Guy]

A combination of non hardening Permatex and teflon makes a very durable joint sealant.

Tim

wrote:

[BIG JOE]

Well, the audible leaks are at an end cap (for future expansion to garage), and the one and only normal coupling (i.e., not a union) in the system. I bought my quick release fittings at the best hardware store in town (UA100 will attest to that), because I'm aware of the quality issues with BORG stuff. They appear to be leak free.

Joe

[BIG JOE]

Ralph Roseburg suggested... You should use rector seal #9 for the sealing compound, depending on the

Funny you should mention that. After finishing up, I remembered I had some other pipe dope laying around, and sure enough, it's the rector stuff I'd used on some garden hose fittings and never had a problem. The stuff I used on the black pipe was greyish and of an inconsistent texture.

I will break down and clean the problem connections and use the rector stuff and maybe teflon tape as well as suggested hear by others. I probably need a bigger pipe wrench as well, mine is only about 15 inches long. When needing two wrenches, I substituted a vise-grip, which never slipped on me, but doesn't give me much leverage.

Joe

[Bay Area Dave]

I've worked with black pipe, PVC, and copper. For air lines, copper is king! :) Seriously, copper is light and easy to assemble leak free with a Mapp gas torch.

dave

BIG JOE wrote:

[Tim Carver]

This makes sense. These can be much harder than unions to get tight, since you often can't use a vise. Why not replace the coupling with a union, and replace the end cap with a union+nipple+endcap made up in a vise (so it will be nice and tight)? Seems like having your endcap on a stub+union would be better for future expansion anyway, you could just replace the capped stub with your new pipe later.

Tim Carver [e-mail]

[Bob Summers]

IME, Teflon tape is not good for gas lines. I put one in my house using black pipe and Teflon tape; I couldn't get the joints to seal, even when I applied enough force with a pipe wrench to make the pipe egg-shaped.

I had to take the line apart and use pipe dope. That worked like a charm.

Bob S

[GTO69RA4]

Was this gas, an in natural gas? There's a special yellow Teflon tape for that.

GTO(John)

[Bob Summers]

It was natural gas. I was using the wrong kind of Teflon tape. But ... if it won't seal air (used for the pressure test) at 15 psi, how well does it really seal. Does Teflon tape depend on the surface tension of water to seal?

Bob S