Trigger Guns, also known as spray guns, are a necessary part of the pressure wash system. Early systems did not have a trigger gun. A hose attached to piece of pipe with a nozzle on the end was all you had. Fortunately for operators the early pressure washer did not have much power. I guess you could put a brick or something heavy to hold the pipe down while you went to shut off the machine. Imagine doing that with 4 GPM of water coming out of the nozzle at 3000 PSI! Hence the invention of the trigger gun.
Generally trigger guns come with a brass 3/8 inch female (F) NPT (national pipe thread) inlet for mounting the hose. A wand is attached to the 1/4 inch FNPT outlet. Hook a gun up to pressure. Pull the trigger to open the gun to start the flow and release the trigger to close it and stop the flow.
Trigger gun operation is quite simple. The handle operates a ball and spring. When the trigger is released the spring holds the ball against a seat, which shuts the water off. When the trigger is pulled the spring relaxes allowing the pressurized water to push the ball aside, which in turn allows water to flow. The trigger gun is designed as a dead man's trigger so if the wand is dropped the water flow stops. Otherwise, with the power of machines today the wand would fly around and do serious damage, if not kill someone. Many operators find ingenious ways to relieve the fatigue of holding the trigger for extended periods of time by using zap straps or tennis balls to hold the trigger open. Not only is this practice dangerous it is illegal in most jurisdictions. For a few dollars more you can get an easy pull style gun, which uses water pressure to assist in the operation of the valve inside the gun.
There are many different styles of trigger guns available
Front Entry Guns
Dump Guns and open guns can be operated without unloader valves because they donít stop water flow. These guns are found in combination steam application where shutting off the steam flow would have dire consequences.
Trigger guns are a maintenance item and should be repaired or replaced periodically. Most manufacturers offer repair kits but at the low cost of a new gun it seems prohibitive to spend money on a repair kit. If a gun leaks when the trigger is released it's time to repair or replace it. That small amount of leaking water will allow the pressure to drop slightly causing the unloader to jump to replace the pressure. This constant cycling is hard on the pump and unloader valve.