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Pressure Washer Guide

Cleaning Power

A rule of thumb when comparing jet washers is to multiply pressure x flow rate and compare the answers (remember to keep units constant). Note: the jet wash with the highest pressure may not be as powerful as one with lower pressure but with greater flow-rate.

Flow Rates

Water usage is normally stated in Litres per minute, or Litres per hour. However, be aware if comparing with American manufacturers, US gallons (3.78 litres) are smaller than UK gallons (4.55 litres).


This can be stated in metric units, i.e. bar, or in imperial units, i.e. psi (pounds per square inch). 14.5 psi is equivalent to 1 bar pressure.

Water Suction

Most jet washers require a mains water supply to the pump. They are unable to suck water. Some models of larger commercial power washers can suck water from a tank. The pumps on these are self-priming. Be aware that many engine driven machines require a mains water supply unless stated otherwise.


When the trigger is released to stop the water flow, the pump continues pumping, but an unloader valve activates to recirculate water through the pump. Some jet washers have an Auto-Stop feature which switches the electric motor OFF/ON as the trigger is operated.

Turbo Lances /Turbo Nozzles

This accessory greatly enhances the cleaning ability of any jet washer. A narrow concentrated jet cuts through stubborn grime at very high pressure (remember pressure is force per area, so smaller area results in higher force). The nozzle also rotates at very high speed to compensate for covering only a small area.

Some typical uses :- Wash barnacles off hulls on boats using very high pressure jet and turbo nozzle. Wash earth and mud from diggers, dumpers, and other construction plant. Clean mud from wheels and tyres on lorries before leaving muddy construction sites. Wash poultry and animal sheds before restocking. Wash agricultural buildings prior to temporary storage of grain at harvest. Cleaning of winter grime and moss from patios, driveways and paths. Pre-foam, wash and rinse vehicles by car valet businesses. Cleaning of oil and grease from engines or machinery prior to repair. Wash dung from cattle floats or horse boxes, and cleaning of stables. Cleaning of lorries between loads. Cleaning of concrete walls, removal of moss from roofs.

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