slow leak - detection?

[Joe Smith]

Friend has an air rifle that has a slow leak. After a week and a half he went to shoot & discovered it was out of air.
I filled it and tried misting with dawn dish soap in water & 'think' I have found a small leak on base of the safety relief valve - very small & hard to see.

Any tips on ways to isolate & find small leaks other than this method?

For tires and stuff that isn't that important I would submerge in a water bath - not sure if it would ruin an air rifle or promote rust in it. If it would not hurt - I can do that - but if something else is better I'll go for it.

Have read of leak detectors that rely on sound - but I am missing all high frequency hearing & in the low range I don't start until about 30% up on the hearing test/charts.(loud noises/military service) So fine settings with these won't really work for me.

Any other way to pinpoint where the leak may be coming from?

I did a search on here but may not being using the right terms as I found three posts that didn't answer the question.

[TroyHammer]

Knowing what rifle. Brand and model is helpful because they can only leak in certain spots. Misting just like you did is my most common method as well but depending on the gun there might be better ones.

[Doug Wall]

Take the action out of the stock and do more soap spraying. Firing valve leaks will show up as air coming out of the barrel.

[SILENT SQUIRREL]

Take the action out of the stock and do more soap spraying. Firing valve leaks will show up as air coming out of the barrel.

Checking air coming out of the barrel is the first test I perform anytime I have a leak
The balloon test is most effective.

just my too sense
Edward

[TroyHammer]

@Joe Smith  Thank you for your service, Brother! I was artillery for 3 years. MLRS and those earplugs didn't help much. I'm with you on frequency and hearing.

[sicumj]

If you have to put it in a bathtub. 

[JPSAXNC]

You can mix up some warm water and dish soap in a glass, dip a Q-tip into the solution and apply it at the fill port and transfer port. That will show if it's the fill valve or the firing valve. HTH

[chuck berry]

I have put more than 1 in the bath tub, then you know for sure whats happening . I oiled first and dried it with a hair dryer. Scary but it does work.I removed the stock, barrel, trigger assembly, and breech.

[kbstingwing]

ultra sonic leak detector if you have the money for a good one, ebay or amazon have them....