Another compressed air line question

[djm999]

I just finished a new copper air line setup in my new garage. During the garage construction phase, I capped most of the outlets so I could test the system. A pressure gauge at the end of the line held constant pressure for several days with no issues.

As I get near completion, I put a couple of threaded disconnects and threaded hose bibs for drainage. I am now getting a slow leak. The lines will go from 120 psi to zero pressure in about 24 hours.

1. Is there a way to find the slow leak?
2. Is it more likely in the disconnects (nothing connected to them) or the hose bibs?
3. Are water hose bibs appropriate for drains or should I have used a gas fitting?

Thanks to all, many of you have been an inspiration for this build.

 

[softailgarage]

water bib? You mean like this?


I would start with whatever it was you used for a drain(s).

 

[jwith68]

Sounds to me like you have a threaded connection leak somewhere. I'd start looking there first, then proceed to solder joints. A ~$1 bottle of kid's bubble making solution and an acid brush makes a pretty effective leak checker. For drains, I used a 1/4" NPT drain **** at the bottom of each drop leg, like this:

http://www.mcmaster.com/#4921k16/=nk4g2k

 

[kbs2244]

My vote would be the hose bibs.
At 120 PSI you are way outside their design envlope.
Replace them with ball valves.

Next would be the threads.
Everybody want to use Teflon tape.
Redo them with blue gasket goop.

 

[Falcon67]

1) soap solution works well, or kids bubble fun
2) Maybe, maybe on the threads too
3) I used all 1/2" iron with 1/2 gate valves above every quick connect and a 1/2 gate valve below for cleaning the drip leg.

This is a typical drop except for the line pressure gage which is only on this particular drop:

 

[toolman1967]

Spay soapy water on all the fittings and valves and you should see the bubbles grow where the air leak is. Simple diagnostic for anything that should be air/water tight.

Tim the Toolman

 

[akdiesel]

I had thread leaks on mine at first. I was only using the Teflon tape, so I used the tape and put some pipe dope on as well.
Since I had multiple leaks at first I figured it would only be a matter of time till the other ones started leaking. So I thread taped and pipe doped them all.

 

[Falcon67]

I had leaks at first and asked a plumber I know what he does for china fittings. He said wrap with tape, then a couple more wraps past what you think is good, then dope, then hope for the best. I have personally JB Welded a few fittings because I didn't want to run to the store and get replacements that might be just as bad. So I might have to saw $5 worth of fittings off a line and trash later, big deal.

Also forgot to add - my system leaks down every 3-4 days from 140 to the trip at 85.

 

[GN4WHLN]

I use ball valves on the drip legs and tank drain in my copper system. I lose less then 5 psi over night. I think the hose bibs are your problem. They probably are not designed for gas pressure.