[anndel]

I have a Husky 33 gallon vertical air compressor I use on pneumatic tools when wrenching on vehicles. I sometimes work late and turn off the compressor but don't release the air from the tank until the next day and it holds the pressure from when I left it, even with the hose still connected (but no tools). There is a leak somewhere on your system and could be the "M" fittings themselves or the drain valve.