Air compressor pipe leakdown question

[lml999]

I had copper pipe run from an air compressor in my utility room to a drop in my workshop and a second in my garage, about 50 feet total. I've got five quick disconnect fittings, all connected with teflon tape in the joints, and two half turn drain fittings in the system.

So here's the question...how long should I expect for the system to maintain pressure after I turn off the compressor? 10 minutes, an hour, days?

I think the system goes from 150 to 40 lbs in about an hour.

I don't hear any obvious source of air leakage. Is this an expected drainage rate for my configuration, or do I have a leak, loose fitting, or bad connector somewhere? What's the best way to find a leak?

Thanks!

 

[ForceFed70]

Mine leaks. Lots of people try for perfection, but it's hard - especially if you are like me and have a couple of cheap hose reels that leak internally.

There's no standard that I've heard of. It's whatever you can live with.

I have a shutoff valve right near the compressor. As I turn the power on/off I also open/close the valve. Works well for me.

 

[lml999]

Mine leaks. Lots of people try for perfection, but it's hard - especially if you are like me and have a couple of cheap hose reels that leak internally.

There's no standard that I've heard of. It's whatever you can live with.

I have a shutoff valve right near the compressor. As I turn the power on/off I also open/close the valve. Works well for me.

Thanks. I don't need perfection...I will not be using the compressor frequently. More curious than anything else...

I went with a Goodyear hose reel in the garage. Didn't think about the reel leaking... I also have a small self coiling hose in the shop. Both are on quick disconnects. The hose in the shop doesn't need to be connected, except when I'm using it. The reel in the garage is just slightly more difficult to disconnect due to the location of the fitting.

I'm hoping to find a specific leak...have to spend some time with the system at full pressure, listening to the fittings. I think the best way to do that, short of borrowing a stethoscope, is to use a piece of 1/4" plastic hose - stick one end next to the fitting and the other up to my ear...old mechanic's trick to find the source of a sound in an engine bay...

There is one potential leak source that I have to investigate...we ran the pipe under a step and when I put the step back together, a nail scraped the pipe. I don't think it penetrated or punctured the pipe, but I'll have to check that out.

 

[flat350]

A spray bottle with soapy water in it will become your friend for chasing leaks.

 

[LS6 Tommy]

I just back off the regulator at the compressor when I'm not using it. I don't lose any pressure in the receiver at all. In use I have no audible leaks in my hoses or reels. One reel is the 50' Harbor Freight and the other is a 25' Costco unit that I have no idea who made.

Tommy

 

[btdobie]

Mine can take anywhere from an hour to a day to leak down. It just depends on the position of the hose reel. Unless there is an audible hiss I won't worry about it.

 

[larry_g]

If you have a shutoff between the tank and the piping shut it off. Then check the leakdown. Quickly confirms if the leak is at the tank or further down line. Un plug all you can that is on quick disconnects, check leakdown again. Do the easy stuff first to try to isolate where the leak is. Then go at it with the bubble juice. Check all fittings and joints. It's not unheard of to have QD's leak. Slide a sandwich bag or balloon over them to see if it blows up.

lg
no neat sig line

 

[EOC_Jason]

Ours never leaked down any noticeable amount even over a period of days or even a week+ in between use...

You should hopefully have a ball valve at your tank, cut it off there, then see if it's the tank dropping or the run. Like other's have said, go at it with some soapy water in a spray bottle... 150 to 40 psi in an hour should be easily detectable. Check the obvious places first like the quick-connects & any filters/drains, then check your soldered joints.

 

[TRWham]

Use thread sealant rather than Teflon tape for a better seal (I use Rectorseal Tru-Blu), and isolate the system near the tank to avoid loss when not in use.

 

[Citation]

Depending on how you use the compressor it may be worth finding that leak. That sort of leak in an hour strikes me as really big given an 80 gallon tank. I also find that 80 gallon tanks need 5-10 minutes to get up to pressure (of course that depends on your pump, rated pressure etc). If, like me, sometimes you just want to put some air in the tires it's stinks to have to wait for pressure to build. I would suggest a shut off valve and using the soapy water to find the leak. If the leak is in the plumbing vs the tank I wouldn't worry as much since you can always shut off the valve. Still, it should be better. My portable compressors don't really leak down. After 1 month I see no significant change in air pressure.

 

[firebirdparts]

If a tube leaks down in an hour that is a tiny leak. If a 60 gallon tank leaks down in an hour that's a big leak.

 

[harleyms]

I've got 150' of 3/4" rapidair maxline with 5 drops and lose about 5 psi a day, I have a shutoff at the tank that is off when not in use.

 

[csp]

Mine has gone for weeks without bleeding down enough to kick the compressor on.

 

[akdiesel]

Teflon should be installed in the same direction the fitting screw on (right hand thread) and approx three wraps and I always use pipe dope over the the tape for two reasons. It lubrates that much more and it helps to seal any imperfections in the threads.
I also use pipe dope on all of my compression fittings and my union fittings on the sealing surface areas.
That was a good detail to use the ballon to find a qc leak.

 

[James-W]

Mine has a very small leak, but I don't worry about it. It is just air leaking, not a big deal. It isn't like I am leaking something dangerous that may kill me or someone else.

 

[ranger302]

My system has about 200' of 1/2" copper and 5 cord reels. It will leak down in about 4 hours. I just turn the valve off at the compressor when I go in at night. The system leaks down and the tank stays full. I am okay with the stress taken off the pipe when I am not using the system. Just my two cents.

 

[ZipSnafu]

My system as a whole will leak down a good bit over night. I have a ball valve at the compressor to isolate it from the rest of the system and has no noticeable leak. It is hard to get a leak free system with today's quality of hardware. Soapy water in a spray bottle is your friend if you want to go for a leak free system. Have fun...

 

[MKSJ]

I use a Rapidair Maxline system, although my previous was all copper. Total runs with ~75' with 4+ drops. In general I see a leak down of 5 PSI/day, and this has mostly been isolated to leakage of the quick disconnects. I do have a real system which is about 25 years old but still seems to hold air without any problem. I strongly recommend adding a shut off valve at the tank and at your distribution manifold (after your filters), I turn the valve off when the compressor is not in use as a hose or fitting may fail.

If with the main manifold valve closed you still are having leakage, and have done the soap test on your connects, then you may have a leak at the compressor tank. The most common source of air leakage from the tank is from the unloadeder valve which prevents backflow of air into the compressor when the system is shut down. They can corrode, or as I found out can have some debris on the sealing surfaces or the spring can fail.

 

[myredracer]

It's not the length of the pipe that's going to cause leakage, it's all the various fittings at filters, regulators, valves, etc. that can. I'd rather have the air leak down overnight and a slow leak isn't going to hurt.

I've got 40-50' of copper and lots of fittings and it leaked down overnight at first. After checking everything with soapy water, I found a male threaded joint into a regulator that was leaking. Wasn't going to be a 5 minute job and I ignored it for a future date. It eventually stopped leaking without touching it tho!! I hate it when that kind of thing happens. Now it takes over a week to completely leak down. If building new, it might help to design it so things can be pulled apart. I've now got a regulator that's acting up from time to time and will need to cut the pipe to replace it, pffft.

Dropped a heavy object on one of my poly hoses recently and split it in almost two. Man, was that a leak or what!

 

[taumac]

I’m one of those the what’s wants minimum leakage as possible. I have a shut of at tank pre manifold, then manifold, and then my hose. I test it regularly and if notice it kicking on with no tools attached then I find the leak. Little spray bottle with dish soap works well. Also might want to check your check valve to see if leaking. Best thing is to have shut off valves to insulate areas. Helps you find leaks and really helps working on areas like replacing parts so don’t have to recharge entire compressor.

I can go weeks without it leaking down. Right now I some worn quick connects so it will last about 2 or 3 days before it kicks on depending on temperature.

 

[lml999]

Use thread sealant rather than Teflon tape for a better seal (I use Rectorseal Tru-Blu), and isolate the system near the tank to avoid loss when not in use.

I used the yellow teflon tape (versus the lighter white tape)...

I will try to isolate the pump and the two individual segments to track down potential leak locations... I'll use some soapy water on each of the joints and connections....

Thanks for all the suggestions!

 

[TRWham]

I used the yellow teflon tape (versus the lighter white tape)...

I will try to isolate the pump and the two individual segments to track down potential leak locations... I'll use some soapy water on each of the joints and connections....

Thanks for all the suggestions!

That may be, but it still will not seal as well as actual pipe thread sealant.