Choosing a Pressure Washer, Hot or Cold – Part 1

If you a looking to purchase a pressure washer here is some guidance to help you choose the right machine for your needs.

All the machines on the market have broadly the same design. They have a motor (electric, petrol or diesel), a 3-piston pump and a length of high-pressure hose with a gun and lance.

The first question to ask is. Do I need a heated machine or will a cold only washer do?

If you just clean the exteriors of vans, tractors or cars then a cold machine will be OK. You will however need to use some detergent to get a good, clean result.

The jobs that a hot machine cleans best are where oil, grease or animal fat needs to be removed. This would include curtain sided vehicles, old engines and animal pens. The hot water will melt or soften the dirt and make its removal easier. Hot water will also make any detergent work better, giving a cleaner finish in a faster time whilst using fewer chemicals. The down sides of having a heated machine are cost and weight. Compared with a cold machine of equivalent power and quality an oil heated machine will be about 3 times more expensive and 3 times heavier. An electric heated machine will be about 4 times more expensive. It will also cost around 3 times more to service.

A hot machine can be oil or electric heated. An oil heated machine has what amounts to an oil-fired central heating boiler under the cover in addition to the pump and motor. It uses diesel, kerosene or heating oil in the burner.

An electric heated machine has large heating elements inside a water tank, similar to those you would find in a kettle. This is heated and then pressurised by a heat tolerant high-pressure pump. Minimum electric requirement is a 3 phase, 415 volt 32-amp socket.

People often ask “what is the difference between a hot water machine and a steam cleaner?” A steam cleaner is an oil heated hot water machine that also has a water flow-reducing valve. When it is used, the amount of water going through the boiler is restricted, allowing it to heat the water to over 100 degrees centigrade. As it is under pressure whilst inside the boiler the water stays as a liquid. As it escapes through the jet at the end of the lance it immediately boils to steam. Steam is useful to remove very greasy deposits and for killing bacteria and other bugs.


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