How to Adjust a Pressure Trapping Unloader

After installing a new pressure trapping unloader it will be necessary to adjust the unloading pressure. The way to begin the adjustment process is to install a pressure gauge at the pump before the unloader for greater accuracy. Once the gauge is installed start the engine without a nozzle in the gun and establish a flow of water through the system thus flushing any foreign materials from the lines. Once you have done this you should install a new spray tip that is properly sized to give you the desired pressure for the gallons per minute that your washer is designed to run, preferably a fan tip. With the new tip installed squeeze the trigger on the gun and monitor the pressure reading on the gauge.

The object of this process is to adjust the unloader until the gauge indicates the pressure that your machine is designed to run while the trigger is depressed and when you release the trigger the needle on the gauge should momentarily raise to a maximum of 300-500 psi above your operating pressure. If as you are adjusting the pressure the needle ceases to rise before the machine reaches the desired pressure you should stop the adjusting process and determine why. You should always know the GPM and Pressure that your machine is designed to run prior to doing any work on it. Use a Nozzle Selection Chart to determine the best nozzle for your purposes or contact a pressure washer repair facility for that information.