When pressure in the tank drops, the pump switches on to try to maintain a certain amount of pressure. It couldn’t keep up with most of our autobody tools; pressure would drop to about 60 psi, and the pump would run continuously. Obviously, this is bad for the pump motor, but it’s also bad for your tools. As it is pressurized, moisture in the air is literally squeezed out and collects in the tank. The more the pump is running, the more the tank fills up. If the motor is running continuously, instead of dropping it to the bottom of the tank, water will start to spray out of the air line. You don’t have to know a thing about painting cars to know that water in your paint will ruin the paint job.