Originally Posted by bonginator
OK - sorry for the laymen's question but this is my first time using my air compressor. Are you saying that when you set the pressure using the pressure control knob on the air compressor that you can set the pressure either 1) while the output nozzle is closed or 2) when you have opened up the output nozzle fully so no air is trapped inside the hose? My understanding is that an air compressor has a tank that fills up with backloaded air pressure and that the knob on the tank controls the pressure of the output. I did not know that you could set the pressure of the output with either the hose open or closed at the time of setting.
There is always a pressure loss from the tank regulator to the end of the hose. Longer the hose, the greater the loss. Same principle for water pressure and electricity (pressure = voltage with electricity, however).
When painting with compressed air, you always measure the desired pressure with the gun open. (with suction feed guns) for this very reason.
IMO, this is not nearly as critical with blowing the lines....just be aware, if you set it at 40 psi with the nozzle closed, you may not have enough pressure with the nozzle open to adequately remove the water.
Jack has it right, IMO.