# Air Leaking From Tank - At My Wits' End...



## DUTCHswift (Feb 22, 2012)

So my tank has been leaking and I can't figure out where its coming from or how to eliminate it.

I have hard lines so my first thought was there. This weekend I pulled all the tubes and put a thin layer of Teflon tape on the ferrules to make sure it wasn't coming from the compression fittings.

The weekend prior to that, I recut (with an airline cutting tool) both of plastic tubes that came from my tank to the manifold and the tube from the tank to the tank pressure sensor and it's still not gone.

I've done a leak test on my bags and I know the manifold isn't feeding more air into them or draining air from them, but I'm still going from 150psi to ~80psi after about 10hrs. The problem is that the leak is so slow that I'm not sure I would get any results from spraying soapy water on my fittings.

I need suggestions on what to do because I'd rather not have my compressors turn on every morning in the winter just to fill up the tank even though I'm not airing out or up in the freezing weather.

:screwy: :banghead: 

My setup:


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## [email protected] (Jan 25, 2008)

Sounds like you may have a bad check valve in your compressor leader line.


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## fasttt600 (Apr 12, 2007)

[email protected] said:


> Sounds like you may have a bad check valve in your compressor leader line.


what Jeremy said. you could also have a leak in the tank itself( and the welds) I had one build where I went through 3 tanks due to weld leaks until I got one that was perfect.

Are you still running the viair check valves? and how long have you had the system?


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## DUTCHswift (Feb 22, 2012)

[email protected] said:


> Sounds like you may have a bad check valve in your compressor leader line.


I took the VIAIR check valves off the leader line and replaced them with SMC check valves so I know they are high quality. Is there a way to check this without going out and spending another $40 on check valves when they might not be the problem? Is it normal for PTC fittings to leak very slowly? I was assuming they were the weak link in the chain.



fasttt600 said:


> what Jeremy said. you could also have a leak in the tank itself (and the welds) I had one build where I went through 3 tanks due to weld leaks until I got one that was perfect.
> 
> Are you still running the viair check valves? and how long have you had the system?


If the tank was really leaking, that would be a brain f*ck. Doesn't airlift certify they are pressure tested and approved? I don't ever remember having this type of leak but I also have been airing out every night up until this point so it wasn't abnormal for the compressors to kick on after I aired up in the morning. The system and all its components are new as of 6/11 this year.


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## SKIDMRK (Sep 15, 2001)

DUTCHswift said:


> I took the VIAIR check valves off the leader line and replaced them with SMC check valves so I know they are high quality. Is there a way to check this without going out and spending another $40 on check valves when they might not be the problem? Is it normal for PTC fittings to leak very slowly? I was assuming they were the weak link in the chain.


take the air filter off of your compressor. put your finger over the compressor inlet hole for 20 seconds or so. pull finger off and listen for air to be released from being built up inside the compressor. this would indicate bad check valve. and SMC check valves can go bad also.

where in the plumbing are your check valves located?


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## euro+tuner (Feb 1, 2007)

DUTCHswift said:


> I took the VIAIR check valves off the leader line and replaced them with SMC check valves so I know they are high quality. Is there a way to check this without going out and spending another $40 on check valves when they might not be the problem?


Put the supplied barb fitting (which are meant to remotely mount your filters) that came with your compressor(s) in place of your filter. Put a balloon on the barb and let it sit overnight; if the balloon inflates at all your check valve is kaput.


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## DUTCHswift (Feb 22, 2012)

SKIDMRK said:


> take the air filter off of your compressor. put your finger over the compressor inlet hole for 20 seconds or so. pull finger off and listen for air to be released from being built up inside the compressor. this would indicate bad check valve. and SMC check valves can go bad also.
> 
> where in the plumbing are your check valves located?


My compressor to tank setup is:

Compressor > Leader Line > SMC Check Valve > 90* Brass Street Elbow > NPT to Compression Bulkhead Fitting > Alum. Tube > Compression to NPT Straight Fitting > Water Trap > NPT to Compression Straight Fitting > Alum. Tube > Compression to NPT Elbow Fitting > Tank



euro+tuner said:


> Put the supplied barb fitting (which are meant to remotely mount your filters) that came with your compressor(s). Put a balloon on the barb and let it sit overnight; if the balloon inflates at all your check valve is kaput.


This sounds like a much easier way of finding out if I have a slow leak out of the compressor. If I only hold my hand on the compressor port for 20sec, it would only be a fraction of a PSI since I'm only losing ~7psi/hr.


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## SKIDMRK (Sep 15, 2001)

DUTCHswift said:


> My compressor to tank setup is:
> 
> Compressor > Leader Line > SMC Check Valve > 90* Brass Street Elbow > NPT to Compression Bulkhead Fitting > Alum. Tube > Compression to NPT Straight Fitting > Water Trap > NPT to Compression Straight Fitting > Alum. Tube > Compression to NPT Elbow Fitting > Tank


gotcha. just wanted to check as i've seen people put check valves right on the compressor head. that heat will melt the plastic internal parts of an SMC valve and cause failure, but doesn't look like that is the cause here.


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## DUTCHswift (Feb 22, 2012)

So I didn't have room to put the barb fitting in there, but I did have room to fit an NPT to PTC elbow fitting on the side. So I put the balloon on the end of the PTC side of the fitting and a rubber band around it so it sealed to the body of the fitting. One of the balloons is already starting to fill up after a few hours and I'm still waiting to see what happens with the other. Awesome idea for checking really slow leaks. :thumbup:


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## northendroid (Sep 16, 2014)

DUTCHswift said:


> So I didn't have room to put the barb fitting in there, but I did have room to fit an NPT to PTC elbow fitting on the side. So I put the balloon on the end of the PTC side of the fitting and a rubber band around it so it sealed to the body of the fitting. One of the balloons is already starting to fill up after a few hours and I'm still waiting to see what happens with the other. Awesome idea for checking really slow leaks. :thumbup:












Most likely there's a piece of debris stuck in the check valve, remove it from the setup and disassemble to clean. Here is a cross section of the valve, the one on the left is the 1/8" and 1/4" ones. If it persist then replace the valve.


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## DUTCHswift (Feb 22, 2012)

I installed some new check valves during my lunch today. Hopefully my tank pressure holds steady from now on and I don't have to go on a ghost hunt to try and find another leak. The car is aired up with 50psi in each corner and the tank settled at 145psi. I put balloons on the compressors again just to verify the problem isn't the check valves again. I'll take a look at it again at the end of the day and let you know how it went.


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## ls150 (Apr 20, 2014)

DUTCHswift said:


> I installed some new check valves during my lunch today. Hopefully my tank pressure holds steady from now on and I don't have to go on a ghost hunt to try and find another leak. The car is aired up with 50psi in each corner and the tank settled at 145psi. I put balloons on the compressors again just to verify the problem isn't the check valves again. I'll take a look at it again at the end of the day and let you know how it went.



Did you use SMC or Viair check valves? Regardless I've found after a lot of headaches that over tightening the check valves, (doesn't matter which brand) will quickly cause the check valve to fail. What I do now is only tighten the check valve hand tight and use a wrench for an eighth of a turn. Ill turn the compressor on to allow pressure to build and check for leaks with soapy water. If there are any leaks Ill tighten the check valve an eighth of turn until the leak stops.


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## DUTCHswift (Feb 22, 2012)

ls150 said:


> Did you use SMC or Viair check valves? Regardless I've found after a lot of headaches that over tightening the check valves, (doesn't matter which brand) will quickly cause the check valve to fail. What I do now is only tighten the check valve hand tight and use a wrench for an eighth of a turn. Ill turn the compressor on to allow pressure to build and check for leaks with soapy water. If there are any leaks Ill tighten the check valve an eighth of turn until the leak stops.


Good idea. One of them is already failing. So I'll pull it off, check the seal, and reinstall with less force. I'm using the SMC check valves as shown.


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## northendroid (Sep 16, 2014)

Did you get your leak resolved?


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## DUTCHswift (Feb 22, 2012)

northendroid said:


> Did you get your leak resolved?


I replaced both check valves and I'm still getting a leak. I'm at a loss as to where to go from here.


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## fasttt600 (Apr 12, 2007)

did you ever test the welds at the tank? I had one build that I went through 3 tanks until I got one without a weld leak. (and that's why I love the seamless tanks. No weld!!!


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## DUTCHswift (Feb 22, 2012)

fasttt600 said:


> did you ever test the welds at the tank? I had one build that I went through 3 tanks until I got one without a weld leak. (and that's why I love the seamless tanks. No weld!!!


How would I go about testing that?


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## ls150 (Apr 20, 2014)

DUTCHswift said:


> I replaced both check valves and I'm still getting a leak. I'm at a loss as to where to go from here.


[HR][/HR]

I would start by removing the blue hose that you have attached to one of the outlets of the tank and capping off that fitting. I would then start doing a process of elimination and capping off different parts of the system until you find the leak. You could also cap off one inlet or outlet of the tank at a time and try to contain the leak to a specific line or group of fitting then test from there.


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## MikuckiMK6 (Jun 25, 2013)

Ive been having the same issue on my girlfriends b7 Passat. I've tooken every fitting off and taped them up again. Sprayed everything and nothing. Has the upgraded valve too.


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## fasttt600 (Apr 12, 2007)

DUTCHswift said:


> How would I go about testing that?


like testing the fittings. spray all the welds with very soapy water. keep spraying it. some of the weld leaks are very small (not like the big bubbles you see with a fitting leak) you will see small bubbles. How much pressure are you loosing over night?


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