Finding leaks

[AV tinker er]

So I was given a compressor by a friend a few weeks ago and after a slight bit of heart burn it is up and running. I have spent some time trying to find a slow leak. The pressure will slowly drop from 125 PSI (60 gal) to ambient in about 5~7 days. I have removed plumbing, cleaned, and applied plumbers tape. I have also used soapy water to see if there are any bubbles forming anywhere. The leak is to slow for the soap trick to work. Is this amount of leakage expected or are there other tricks/steps I should take?

 

[dhill001]

I've had good luck using full strength high quality dish soap undiluted. It is thick enough to stay in place at fittings and the bubbles don't pop too soon to see them. You might see foam rather than a single bubble.
My back of the envelope calculation of 125psi (8.5atm) times 60gal divided by 6 days is 13 cubic inches per minute. That should be enough to blow a pretty good bubble if it is occurring at only one place.
Have you used the soap trick on the overpressure relief valve and your (I assume you have) quick connect fittings?

 

[dieselgarage]

Using soap it's hard to find small leaks.

http://www.amgas.com/ltpage.htm

Most hardware stores have it for finding gas leaks.

 

[Alta_Racer]

Check valve

 

[DirtRoad]

Using soap it's hard to find small leaks.

http://www.amgas.com/ltpage.htm

Most hardware stores have it for finding gas leaks.

This^

The soap trick has never worked for me either. The leaks are normaly so slow it wont make bubbles or foam.

 

[readhead]

Check the pressure switch and the drain. Check everything on the pump also. I use windex.

 

[MrMark]

Soap is not good for small leaks. There is also a Hercules product avail at Home Depot that works well for this.

 

[SCTony]

Check valve

^^^ That is what my hard-to-find small leak turned out to be. My pressure switch diaphragm was leaking too.

 

[Tim The Tool Man]

Check valve

^This +2 or a pin hole in the bottom of the tank due to rust... I hope not the latter!

 

[Falcon67]

I call - normal. Good luck sealing it up tight. For my joints, I know a plumber and his advice was about 4 more wraps of teflon tape than you'd think, paint with thread sealer, then install. I can't find any leaks and my pressure switch will trip on about every 5 days or so. Check valves, pressure switch, drain, etc, etc. Even the pressure rated gate valves leak a little. Best advice from here is a gate valve at the compressor, close it when you leave to shop.

 

[Fixnair]

X2on the check valve. Almost impossible to detect. With pressure in the tank, disconnect the discharge pipe from the compressor and the check valve and bubble test it.