How Do I Troubleshoot Karcher Pressure Washer Surging?

spray jet image by David Levinson from

Karcher is a German manufacturer of several types of cleaning and maintenance equipment for residential and commercial users. Chief among these products is a line of Karcher pressure washers, of which there are many model types with varying features. Karcher pressure washers have either electrical or gasoline power.

If your Karcher pressure washer experiences surging of its spray or intermittent high and low pressure, you should do a bit of light troubleshooting to determine whether the issue is due to a number of common factors, each of which can be corrected with light basic maintenance to the pressure washer unit.

Ensure that there is sufficient water flowing into the pressure washer inlet valve by using a 3/4-inch-diameter supply hose and turning the water spigot to its maximum flow rate. You want a flow rate of at least 2.5 gallons of water per minute to ensure an even stream of water and to reduce wear on the motor components.

Confirm that the pump is sucking in just water and not air by tightening down all of the hoses, fittings and couplers. Shut down the pressure washer motor. Squeeze the washer wand trigger until a steady and even flow of water comes out of the nozzle. This clears the system of air bubbles. Turn the power washer back on.

Remove and rinse the water inlet filter with a strong stream of warm water to remove any sediment or deposits trapped there that may intermittently be interrupting water output and causing surging. Replace the filter and operate the power washer normally.

Clear any debris or build-up that may be obstructing the spray nozzle by sliding a sewing needle into the tiny opening at the tip of the nozzle. Push the needle in and out several times and jiggle it around gently to dislodge any build-up or blockage. Run water through the system to blow out any loosened material.

Dissolve calcified deposits in the spray gun, nozzle and hosing by running white distilled vinegar through the system to dissolve and loosen build-up. Slide the open end of the detergent suction tube into a bottle of distilled white vinegar and squeeze the detergent lever until the bottle is empty. Run clean water through the system to rinse out the vinegar and the loosened deposits.