Sometimes a compressor regulator is leaking. Understanding that general purpose air regulators are sometimes supposed to leak may set your mind at ease. Or, you might have a regulator problem.
General purpose air regulators are typically relieving regulators. This means that they can leak on purpose. That purpose is to allow higher pressure downstream from the regulator to bleed back up and out of the regulator when the regulator is adjusted to a lower downstream pressure.
If regulators did not self-relieve, when the pressure setting was dialed down from 90 PSI to 20 PSI, for example, even though new air flowing into the air line should be at 20 PSI, the air already in the air line is at the original 90 PSI. If the application was pressure sensitive, a burst of too high pressure air from the line may cause a problem.
If you have an air line plugged into the coupler on the compressor, and you dial the pressure setting of the regulator downwards, higher pressure air from the air line can be heard leaking from the regulator. That leak will continue until the pressure downstream of the regulator is at the same pressure level as the new regulator setting.
Sometimes the regulator is leaking
A new, general purpose regulator, can usually be purchased for $15-$20.
If the regulator sells for $15-$20 retail, it’s a pretty good bet that the actual manufacturing cost of the regulator is way below that, perhaps in the $5 range or even lower. Can you get really good quality components when the whole regulator may only cost $5 to make? Nope!
The item inside the regulator that keeps the air flow from leaking out is the diaphragm. This regulator part flexes constantly as the compressed air flows through the regulator body, fluctuating to exert more or less pressure on the internal spring of the regulator as it works to maintain a constant downstream air pressure at the regulator setting.
Typically some sort of rubber compound, the diaphragm can be attacked by oil and crud in the air stream from the compressor, causing it to lose flexibility. Ambient heat also has an affect. The higher the air use, the more the regulator diaphragm is stressed in the process of regulating the air.
In time, the diaphragm will crack, and then the regulator is leaking.
Regulator not leaking all the time?
A cracked diaphragm may not leak all the time. At lower pressure settings, the stresses involved with regulating the air may not be enough to force the crack open in the diaphragm.
The diaphragm may only leak at higher pressure settings.
Not the regulator diaphragm
A regulator leak may not mean a cracked diaphragm.
There are typically a couple of “O” rings inside of and on the stem of the regulator. Over time, these may become brittle to, and allow air to leak.
Fix it when the regulator is leaking
In my case, I cannot get excited about tearing down the air regulator when it is leaking, to try and figure out what part has failed, then have to spend the time to try and source the part and acquire it.
The hardware or specialty store where the compressor was purchased likely does not stock parts.
Even though regulator spare parts can be found on line, by the time the shipping is included in the equation, buying the part may cost equal to or more than the cost of the whole new regulator.
What I’d do then if I wasn’t sure about the replacement, is remove the regulator from my compressor and take it with me to the hardware store, to fine a comparable replacement.
By comparable replacement I mean a new regulator that has the same thread size, the same pressure range, mounting method, and a similar body size to the old.
Oh, and for the $15 bucks or so, you’ll normally get a new air gauge to go with the new regulator.