Slooooow Air Leak

[Ken Whitney]

I just finished plumbing the last two legs of my compressed air system. It is copper pipe.

I had two audible leaks when I pressurized the system, but I re-soldered these joints and when the lines were re-pressurized there were no audible leaks and the system appeared to hold air fine.

However, I lose about 5 psi every couple of hours or so. I tried the soapy water test on the new joints but didn't see any detectable leaks. Is there another method to detect these small leaks?

Is it worth re-soldering the joints one by one to see if the leak diminishes, or is this rate of loss not worth worrying about?

I do close the main supply valve at the tank when the system isn't being used, but I hate to have the compressor come on in the middle of the night when I forget to close the valve.:)

Thanks.

[Nathan Hawkes]

I'd say that 5psi in 2 hours is definitely something worth fixing, if it is hardwired. That compressor is going to cycle on/off at least once a day when you're not using it. If you're sure it isn't any of the joints, it is likely in the hose fitting connection. I replaced the quick-change connector recently on my hose, along with the maple fitting on my air nozzle. If it were left in just the right position, I could hear air slowly leaking out if I held it right to my ear. It took a little searching to discover it, just like your situation. The "listen" test was the last spot! This wasn't quite as bad as the leak you're describing, but almost. I noticed about 10psi drop overnight in a 35 gallon tank. If you still can't find any leaks anywhere, it is quite possible that the leak is in the shutoff valve itself. If it's a ball shutoff valve, chances are that the o-rings seat just fine in the "off" position, but may be loose enough around it to leak when they aren't compressed in the "on" position.

[Ken Fitzgerald]

The soapy water trick will almost always do the trick....unless the leak is on or in the compressor....

In other words...check all the connections on the compressor with soapy water....

If you are using quick disconnects on your hoses....try checking it with the hoses plugged in and not plugged in..... A quick disconnect will leak....


The problem could be internally within the compressor if all other things check out.

[Tom Hamilton]

Ken, you can also put a timer on your compressor so it comes on and shuts off at times you choose. They are readily available and cheap now in the Christmas lights sections of most stores.

Best regards,

Tom, in Douglasville, with a compressor that's on from 8AM to 6PM.

[Leo Van Der Loo]

Ken I second what Ken F. is saying, try every joint with soapy water, to make sure they do not leak, it is quick and easy and does away with any question of is there maybe another leak somewhere.
most compressors that I worked with did have a valve that would close by weight and pressure between the tank and compressor, if there isn't one then the air will almost surely leak back through the compressor, the other thing, as was mentioned, is that quick connects do leak, a good idea is to have a good quality ball valve before the quick connect, just a quarter turn and you do away with any leak there or in the hose and other pieces connected to it, after doing that, there should be no pressure drop, and your system could sit for days without loosing any air at all, HTH

[ray hampton]

soapy water works fine on one condition, the soap+water mix
need to stay on the fitting, I use straight liquid soap which will
stay on the fitting even when applied to a fitting that are up-side down

[Greg Ketell]

Sounds like you only soaped the two fittings that you know were leaking. You have to soap them all.

I've also run into situations where a length of pipe leaked air. Held water, but leaked air. Go figure. If none of the joints show a leak, soap it all.

If you have a shut-off valve at the head of the compressor, add a gauge to the line somewhere, charge the line then shut it off at the compressor. If the pressure goes down you know the leak is in the line or in the shut-off valve (outside half). If the line stays pressurized you know the leak is in the compressor or the shut-off valve (inside half).

Good luck!

[Greg Bender]

Ken,
make your own soapy solution with about a 4 to 1 ratio of water tto soap.It needs to be like kids bubble solution so it clings and will inflate over a leak.Check every connection with it charged to your compressor's max rating.You could have a leak at high pressure that diminishes at lower pressure levels.In work,IR, we use a hand held gun and headphones that is very sensitive but I would not know where you would find one.How are your solder joints ,are there any that look dull or cold.If you visually see any that aren't shiny I would redo those joints.
my .02,
Greg

[Ken Whitney]

Thanks all for the great advice.

I'm pretty sure the tank and compressor are OK. It is an 80-gallon tank and I have a ball valve at the tank outlet. When closed, I get no pressure loss.

Unfortunately most of the solder joints are up in the garage rafters and probably not the shiniest and best joints, so I will head back up and do the soap test again.

Also, I did not check any of the fittings, and I do have quick connects, so I'll check everything, soldered or not, and see what I can find.

Thanks again. I'll report back with any progress.

Ken

[Faust M. Ruggiero]

Quick connects will almost leak a bit. I install ball valves ahead of each quick connect and shut them off when I am not using that particular drop.

[Mary Thompson]

Check the tank drain on your compressor, it often gets overlooked.

[Ken Whitney]

Thanks again to all for the advice.

I rechecked joints and fittings and found a leak. I had attached a filter/regulator via a union, and it needed to be snugged up a bit.

The soapy water test (I used a 1:1 mix) worked very well.

I hope that this turns out to be the leak rather than a leak.

Ken

[Jim Underwood]

5 psi per hour? Heck that's pretty good!

I bet my water separator drains more than that...:D

You do have a water separator don't you?:cool:

[Ken Whitney]

Water separator? I don't need no stinkin' water separator!:)

Actually, I have four air connect points, two drops to drain the line, plus a filter/separator/pressure regulator. I only have a 12x25 shop, so I may be slightly over-plumbed for air.

And it is six hours and counting without a noticeable drop in pressure. Keeping fingers crossed.

Ken