I just finished my copper air lines for my air compressor. I have 5 drops using Milton quick disconnects. At each I have a drip leg for any water condensation and a conbraco ball valve at the end of the drip leg. There is a union in the middle of the drip leg. I still see a very small pressure drop over a day's period. Wondering if this is normal and expected? I've used bubble type leak detection at each solder joint and each threaded joint and see no bubbles. But I'm thinking small leaks could be happening at the ball valves, the unions, the milton quick disconnects and also at the hose connecting the compressor to the filter regulator (these are Pneumatic plus brand). What's your experience with similar setups?
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Air system leaks - large vs small
- Thread starter thammel
- Start date
It is damned hard to prevent all tiny leaks. I figured if I had the leaks down to where the compressor runs only once a week if not used I was good. That is about where my current setup is.
I have seriously considered a ball valve with a 120 volt actualtor at the outlet of the tank. Connect it to the lighting circuit in the shop so tha ttank is isolated from the piping when not in use.
I have seriously considered a ball valve with a 120 volt actualtor at the outlet of the tank. Connect it to the lighting circuit in the shop so tha ttank is isolated from the piping when not in use.
Your air lines are far too complicated to be anywhere near 'leak free'. That you're only seeing "a very small pressure drop over a day's period" indicates to me that you've done a very good job and, as such, you shouldn't worry about it.
Last edited:
rlitman
Well-known member
I have one of these on the valve coming off my tank:
I shut it when I'm not using air. The rush of air out of it is hard on the regulator, but I don't waste money running the pump if I don't use air for a week.
I shut it when I'm not using air. The rush of air out of it is hard on the regulator, but I don't waste money running the pump if I don't use air for a week.
Don't split the atom. If it isn't at least an audible leak, let it be. I've found that over time quick disconnects start to leak a little, especially if there's lateral load. Just shut the compressor off when you leave so it doesn't run all night.
Firebrick43
Well-known member
Most disconnects leak a small bit, only ones I have seen that down are the oatiker swing ones. I have never used the stedlins so I don't know about them. I should try them some time.
nadogail
Well-known member
IMHO, Pneumatic Systems all leak a little bit. You seem to have reached that point.
Cooling of heated air will reduce pressure in the system over a days time. Plot your daily loss over a weeks time if you can to find your leakage rate on a stable system. Also don't ignore leaks withing the compressor itself at the chack valve and the pressure release.
lg
no neat sig line
lg
no neat sig line
fastev
Well-known member
I’m with Larry. I suspect it’s due to heat loss of the compressed air, not a leak.
Your heat sink is huge in the copper distribution piping. In a typical unconditioned garage I wouldn’t be surprised to see a few psi fluctuation, up or down, in a 24-hour period.
Basically, don’t worry about it.
Your heat sink is huge in the copper distribution piping. In a typical unconditioned garage I wouldn’t be surprised to see a few psi fluctuation, up or down, in a 24-hour period.
Basically, don’t worry about it.
Thanks so much for all your replies, guys! The way I test for the leak is to valve off the compressor and watch gauge pressure vs time. It dropped from 70psi to 60 psi in about 5 hours or so. The compressor is really airtight. Valved off, it holds pressure steady. Yep, with all the disconnects, valves and unions, I guess I have to expect some small losses. In my engineering career, we measured leak rates with helium leak detectors and I know any elastomeric item will permeate gases. So there is the connection hose and all the o-rings sealing the quick disconnects, etc. Guess things are ok. I really brushed up on my soldering skills - I counted 102 solder joints!!! LOL!
walta
Well-known member
If you really want to find the leaks fill the system with water under pressure and the leaks will show themselves.
Walta
Walta
Firebrick43
Well-known member
air molecules are smaller than water molecules. Water is something like 90 times more viscous than water. That is why water lines are pressure tested with air. Air with a good leak detecting solution like snoop will show up and water will not.If you really want to find the leaks fill the system with water under pressure and the leaks will show themselves.
Walta
30 psi air testing is the equivalent of 150 psi water testing for leaks
Walkers
Well-known member
Most likely the unions and QDs. It is not difficult, nor exacting to have a leak free system. I piped many a natural gas system at anywhere from 1/4 Lb to 3000 pounds and they all test leak free. Learning how to soap fittings is not as easy as you might imagine though, there is some technique involved.
Though my own piping system is leak free, it is not leak free 100% of the time. QDs start wearing out, or have a little piece of dirt on the rubber seat, hose reel swivels are known leakers. If a ball valve leaks you either are over pressuring it, or something happened to it (the solder on ball valves are the worst offenders), but if it is a threaded ball valve it shouldn’t leak at all.
My compressor is on a switch, it gets turned off at the end of every day. Most days nothing happens when I turn the switch. Every once in a while the compressor kicks on. I never leave it live while the shop is closed. I had a little 3 horse and got home at the end of the day and heard a noise in the shop. The little compressor was puking it’s guts out trying to keep up with a burst hose. That little problem cost it its’ life, as they need pressure to push against to keep their oil. My current compressor is 100% duty cycle and could likely keep up with a burst hose, but it is expensive enough to not want to find out.
Though my own piping system is leak free, it is not leak free 100% of the time. QDs start wearing out, or have a little piece of dirt on the rubber seat, hose reel swivels are known leakers. If a ball valve leaks you either are over pressuring it, or something happened to it (the solder on ball valves are the worst offenders), but if it is a threaded ball valve it shouldn’t leak at all.
My compressor is on a switch, it gets turned off at the end of every day. Most days nothing happens when I turn the switch. Every once in a while the compressor kicks on. I never leave it live while the shop is closed. I had a little 3 horse and got home at the end of the day and heard a noise in the shop. The little compressor was puking it’s guts out trying to keep up with a burst hose. That little problem cost it its’ life, as they need pressure to push against to keep their oil. My current compressor is 100% duty cycle and could likely keep up with a burst hose, but it is expensive enough to not want to find out.
I was thinking of one of these, wired into the lighting circuit.
https://www.ebay.com/itm/301845492201
I already have the compressor motor's motor starter wired through a relay that is in turned wired to the lighting circuit. No lights, no compressor.
I used to do the manual ball valve, but I would forget, and one time came home after being gone for a couple days and a air line split so the compressor had been running for quite some time. That is when I went with the shut off tired to the lights. I don't forget to turn off the lights!
https://www.ebay.com/itm/301845492201
I already have the compressor motor's motor starter wired through a relay that is in turned wired to the lighting circuit. No lights, no compressor.
I used to do the manual ball valve, but I would forget, and one time came home after being gone for a couple days and a air line split so the compressor had been running for quite some time. That is when I went with the shut off tired to the lights. I don't forget to turn off the lights!