Never allow a pressure washer to run for more than 2 minutes with the trigger gun closed. This will overheat the pump resulting in expensive pump repair or failure.
Hot water pressure washers are a wonderful source of hot, convenient, inexpensive hot water and pressure. Turn on the unit, hit the burner switch and you have instant hot water for cleaning your equipment, floors or fleet. The advantages of the hot water pressure washer make it a common tool for many facilities. It becomes an integral part of your operation and everyone depends on its reliability to be ready to operate at a moment’s notice. The hot water produced provides much quicker cleaning results and is a must when dealing with oils and grease. The heat left unchecked, however, can also destroy the very equipment you rely on.
All pressure washers work the same way. You need a pump to move the water at a certain flow, a coil to heat the water and a nozzle to pressurize the water. Everything else on the machine is there to make these components work the way you want them to, and to provide safety.
The pump, which is driven by an electric motor, gas or diesel engine, draws or accepts filtered water through a series of inlet check valves as the plungers move back. As the plungers move forward, the inlet valves close, forcing the water to travel through a series of outlet check valves to the outlet side of the pump.
After the water exits the pump, its flow direction must be controlled with an unloading or regulating valve. The pump is always delivering a certain volume of water whether the spray gun is open or closed, therefore a device is needed to control the direction of flow, either allowing the flow to go through the open spray gun or redirecting (by-passing) the flow back to the inbound side of the pump when the spray gun is closed. The trigger spray gun and unloader valve are the two most common safety components for high pressure cleaning equipment. Depressing the trigger allows water to flow out of the system through the nozzle under pressure while releasing the trigger diverts water flow back to the inlet of the pump. Remember, the pump continues to run during either of these events.
When the trigger gun is closed to stop the flow, the pump is still working to produce the rated flow and pressure. The total volume of water being recirculated is less than a half gallon. As that water bypasses from high pressure (the outlet side of the pump) to low pressure (the inlet side of the pump) it creates frictional heat. If the unit is left in bypass for an extended period of time, that bypass water can reach temperature levels in excess of the boiling point. At this point the pump seals and oil seals are destroyed, the check valves are destroyed, the ceramic piston sleeves are in danger of cracking, and chances are the bypass hose will fail as well.
It is vital that your unit not be allowed to run in bypass for periods longer than 2 minutes. You can protect against this expensive failure by training employees to properly shut down the unit upon completion of the work. Any time an employee is going to release the trigger gun and walk away from using the pressure washer, the employee should turn the pressure washer off to avoid the build up off heat in the pump and costly repairs caused by extended bypass.