Ever wonder how to test your compressor tank check valve? Or even, why bother testing your compressor tank check valve?
What are the symptoms of a faulty compressor tank check valve?
When your air compressor stops after filling the tank, the compressor line from the pump to the tank becomes open to atmosphere. This is to ease the load on the pump the next time the compressor stops.
It is the compressor tank check valve that is in place to trap the air in the compressor tank, so that it does not bleed out of the tank back up the line from the pump, over to the unloader valve, and out to atmosphere.
In the image below we have a couple of typical air compressor check valves.
The compressor tank check valve is commonly threaded into the compressor air tank. The threads that are coated in reddish pipe compound are turned into a mating port on the compressor tank itself and tightened snugly.
Port 1 is where the line from the pump head would be attached to allow the compressed air to flow from the pump into the compressor tank.
Port 2 is where the air line that is plumbed over to the unloader valve is attached. These are compressors with an external pressure switch which may have an unloader valve on the side of it, or an internal unloader. While air is being pumped into the compressor tank through the port 1, the unloader valve is shut, so the compressed air cannot flow along the air line attached to port 2 and escape to atmosphere.
Port 3 is where the air from the compressor pump escapes from the tank check valve and into the compressor tank. It is within this part of the tank check valve that the actual check valve or flapper valve is housed.
When the compressor tank check valve leaks
If the check valve or flapper valve in the bottom of the tank check valve assembly becomes fouled up or breaks, air can escape from the tank. A typical indication of this is when the compressor stops, after unloading the pump, the unloader valve continuously leaks air.
That leaking air has to come from somewhere, and that somewhere is the compressor tank.
If that happens you need to test the tank check valve.
How To Test Your Compressor Tank Check Valve
… blow into it. Yup, that’s how we test them.
Wipe the shank of the tank check valve up to the tank threads, wrap your lips around the valve below the tank threads, and blow.
If the tank ball check or flapper valve is good, no air should exit either ports 1 or 2. None.
If air leaks out of either of these two ports, your check valve is not seating, and that’s the source of the leak out of the unloader valve.
Try washing the valve in hot, soapy water, rinse thoroughly, and dry completely. Test again. If it still leaks, replace it.