pressure washer makes a loud knocking or banging sound when i pull the trigger, is it broken?

Diagnosis

The loud knocking or banging sound you hear when engaging the trigger is a classic symptom of pump cavitation and air entrapment. This occurs when the AR Blue Clean AR383 pump attempts to draw water that isn't available at the required volume or pressure. This creates a vacuum inside the pump head, causing tiny air bubbles to form and then violently collapse. These "implosions" create the mechanical hammering sound you are hearing, which can eventually pit the internal pistons and destroy the valve seals if left unchecked. This is rarely a sign that the motor is "broken," but rather that the pump is being starved of water. The root cause is typically a restriction in the supply line—either a kinked hose, a clogged inlet filter, or a water source that cannot keep up with the AR383's flow rate. You can confirm this by checking the water stream; if the spray pulses or "sputters" in synchronization with the knocking sound, you have a definite air-lock or supply restriction issue.

How to Fix It

To resolve cavitation and stop the banging, follow these steps to ensure a laminar, unrestricted flow of water into the pump:

1. Purge the Air: Turn off the machine. Connect your garden hose and turn the water supply on fully. Squeeze the trigger on the spray gun and hold it for 30 to 60 seconds while the machine is still OFF. This flushes all trapped air out of the pump head and hose lines.
2. Clean the Inlet Filter: Locate the water inlet connector where the hose attaches to the AR383. Using a pair of needle-nose pliers, carefully remove the small mesh filter screen seated inside the inlet port. If you see any sediment, algae, or grit, rinse it under a high-pressure tap or use a soft toothbrush to scrub it clean. Reinstall the filter securely.
3. Optimize the Supply Hose: Ensure you are using a reinforced 5/8-inch diameter garden hose. Avoid using "expandable" or "pocket" hoses, as these often collapse under the suction of the pump, restricting flow. Limit your total hose length to 50 feet; any longer, and the pressure drop may cause the pump to starve.
4. Verify Source Pressure: Ensure your home spigot is opened to the maximum position. If you are using a rain barrel or a gravity-fed system, the AR383 will likely cavitate because it requires a pressurized feed to function correctly.

If That Didn't Work

• Check for an Air Leak in the Inlet Fitting: If the hose connection to the pump is not airtight, the pump may suck air into the system even if the hose is full of water. Replace the rubber O-ring or washer inside the hose coupling to ensure a vacuum-tight seal.
• Inspect the Unloader Valve: The knocking could be caused by a sticking unloader valve. With the machine off, spray a small amount of silicone-based lubricant into the unloader assembly to ensure the internal spring and piston move freely without sticking.
• Check for Kinks in the High-Pressure Hose: While less common, a severe kink in the outlet hose can create back-pressure waves that manifest as a knocking sound in the pump. Ensure the high-pressure hose is laid out straight without tight loops.
• Test with a Different Water Source: If you are on a low-pressure well system, try connecting the unit to a different faucet. If the banging disappears, your primary water source is unable to provide the GPM (gallons per minute) required by the AR383.

Heads Up

• Never Run Dry: Running the pump for even 30 seconds without water can overheat the seals and cause permanent damage to the ceramic pistons.
• Winterization: Always drain all water from the pump head before storing the unit in a garage or shed during winter; frozen water will crack the pump manifold.
• Filter Maintenance: Clean the inlet screen every 10-15 uses, especially if you have hard water or a well with sediment.
• Avoid "Trigger-Happing": Avoid rapidly squeezing and releasing the trigger (pulsing), as this can create pressure spikes that stress the internal valves.