Tank Will Not Hold Pressure
If you notice that your tank is not holding or losing pressure, the most common cause is, of course, a leak. So, the first thing you want to do is a soapy water test. What is a soapy water test? If you have a small leak, you may not be able to see or hear where it is coming from. The best way to find the leak is to fill a spray bottle with water and a little bit of soap and spray down your system.
Anywhere that you see bubbles start to appear will be the location that your leak is coming from. Make sure you spray around any and all connections, such as the ports on your tank and where your airline connects. Also, make sure your drain cock is closed (you may have just forgot to tighten it back up after the last time you drained your tank).
If you don’t find any leaks on your system, the leak may be coming from your compressor (which you wouldn’t be able to detect with a soapy water test). Check the near the filter of your compressor to see if you can feel any air coming out of the filter. Air is supposed to be sucked in, not blown out of the filter area, so if you notice any blowback, that is a good indication that either your compressor or check valve needs to be replaced
The check valve on your system is a fitting attached to the end of the metal hose (called the leader hose) that is attached to your compressor. It plumbs into your tank and is responsible for ensuring that air goes into your air tank and not back through your compressor. While it is much more common for you to over-torque your check valve and break it during installation, they may have to be replaced after a long period of time do to wear and tear. The easiest way to check to see if your check valve needs to be replaced is to blow in it. Seriously, if your check valve is broken it will let you blow air back into the leader hose. If it works, it won’t let any air through in that direction. If you check valve is working fine and you are still seeing blow-back from the compressor, unfortunately it may be time to replace the compressor.