Which Diesel Pressure Washer?

Which Diesel Pressure Washer.

Choosing a Diesel powered pressure washer offers you the ultimate power & performance available from a high pressure cleaner.

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Diesel Engines

Engine sizes vary from 7 to 10 HP units, the 10 horse power unit being the most popular in the UK. They are 4 stroke engines which means, they need oil in the engine sump. Diesel engines give much better torque than petrol engines and are widely used where longlife & heavy duty use is required. Diesel engines are also more economical on fuel; so where long periods of use are involved this can be a cost advantage. Sometimes they are coupled directly to the high pressure pump, though some can have a reduction gearbox in between.

reduction gearbox kiam A Reduction gearbox is usually found on the more powerful models where the intended use is for long hours and heavy duty work. The other benefit of a reduction gearbox is that the pump runs at a much slower rpm (1400 rpm) meaning that it is easier for the pump to suck water from a standing source ( water tank)  - so theres no need for a mains supply.

Pump Types.

Industrial Pumps are normally made from Brass, and are of two types... the Axial design ( on smaller machines) and the popular crank pump, featuring 3 pistons that are normally fitted to heavier duty diesel machines.

The power of the pressure washer pump is determined by the operating pressure and the amount of water it can pump. Pressure is measured in either Bar or PSI (pound per square inch) with one Bar equal to 14.5 psi. Water flow is measured in L/m (litres per minute). The combination of the pressure & flow rate is what gives you the cleaning power. One is no good without the other.

Starting Methods.

Diesel engines can be started by a pull cord, or usually by electric key start. It is normal to hold down the compression lever for a few seconds whilst turning the key over, inorder to spin up the engine off load, to help it start easily.


For Industrial cleaning jobs... as the saying goes .. " the bigger the better". So the 10 Hp engined units will give the best performance; up to 3500psi @ 15 litres per minute. At these pressures - they'll shift heavy dirt & debri from agricultural plant, boats, HGV's & industrial equipment. Their most popular use would be for Professional Driveway Cleaning; where the pressure washer will be used for up to 8 hours a day, giving reliable, powerful performance.

The other benefit of greater performance is the fact that any accessories you connect to the petrol pressure washer - such as a drain cleaner, turbo nozzle or rotary cleaner - will work far better on a more powerful machine. This means you'll get the job done a lot quicker too.