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In most pressure cleaning equipment, the pump motor is turned on and off at the machine. The operator, however, may be cleaning as far as 100 feet away. When he wants to stop spraying water he needs a way to stop water flow without walking back to the machine. The trigger gun and unloader provide that kind of control literally at the operator’s fingertips. The valves in the trigger gun and unloader can be thought of as a pair of traffic cops, directing the "traffic flow" of water in the cleaning system.

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 to the system through the nozzle under pressure while releasing the trigger diverts water flow back to the inlet of the pump. The pump, however, continues to run. Today, a number of automatic systems have been developed which allow for complete pump and power shut off when the trigger spray gun is released. However, none of these systems are used as widely as the unloader.

Benefits of A Spray Gun System
• Safety: prevents the wand from getting out of control and causing damage or injury.
• Convenience: Allows the operator to turn the spray on and off.
• Economy: Diversion of flow to bypass saves water and chemical. Complete system shutdown saves fuel and power.

The Trigger Spray Gun
A trigger spray gun is nothing more than a valve that closes when the trigger is released. Spray guns are fairly simple mechanisms designed around a trigger-operated valve. Generally a ball valve is used in trigger guns but a piston valve may be used in a dump gun. In a trigger spray gun, the valve ball is held in a closed or forward position by the flow of water and blocks the flow of water through the gun to the nozzle. When the trigger is depressed it pushes a pin against the ball, forcing the ball out of its seating and opening a path for water to flow to the nozzle. When the trigger is released again a spring returns the ball to its seating and the flow is again blocked. Flow blockage actuates the unloader on the outlet or high side of the pump and water is diverted back to the pump’s inlet or low side, reducing pressure at the spray gun.

Trigger Gun Benefits
• Puts water into bypass.
• Works with flow or pressure unloader. Actuates flow and pressure switches.
• Allows remote control of water flow.
• Spray gun grip gives the operator better control of the lance.
• Makes the high-pressure lance safe if the operator loses control.
• Makes a walk back to the pump switch unnecessary in most situations.

Spray Gun Types

There are two main types of spray guns. The Flow-Through Spray Gun passes water all the way through the spray gun and the valve is above the trigger. This spray gun reduces operator fatigue because of its configuration and lighter weight. Overall it is bettered built and more expensive. The Front-Entry Spray Gun can handle higher temperatures since the water does not flow through the handle and is a simpler design, so is consequently less expensive. One drawback to the front-entry spray gun is the weight added when the hose is connected in front of the trigger, causing the user to be off balance. Spray guns come in a wide range of flow, pressure and temperature ratings. A fairly standard heavy-duty gun design will generally be rated for 4,000 + psi at 300 degrees Fahrenheit and a 10 gpm flow.

Remember: Equipment should not be operated at pressures above the pressure rated for the system. Do not use a smaller nozzle than recommended for the system to increase output pressure.