How to use a pressure washer with detergent

June 30, 2022 @ 6:29 am

How to use Detergent with a  pressure washer

It is fair to argue that doing the washing-up is much easier when you are using washing up liquid/detergent as well as water. The same can be said about adding detergent to your pressure washer when you want to get some important cleaning done outside.

 But no one ever really explains how to use pressure washer detergent properly

Well, of course, a pressure washer will lift huge amounts of dirt off the surfaces of your decking, garden tools, and car, if done correctly and safely.

However, adding the special cleaning properties of soap or detergent will give that extra boost to your cleaning results for those really, ground-in stains.

Soap and detergents are so-called ‘surfactants’ – they interact with oil and grease enabling surface tension with water more easily.  In other words, they connect, at one end with dirt/oil and the other with water. 

This enables the water to pull the dirt/oil away from the surface of whatever is being cleaned and, let’s face it – every little trick to help is a welcome one when it comes to cleaning.

Quite simply, using detergent when pressure washing is a straightforward part of the process. The difference is in how you apply the detergent.

There are a few different ways. And how you do it, will probably depend on the type of pressure washer you have access to.

By Hand

You might want to consider the most simplistic way to add detergent to your pressure washing and that is by adding your detergent, by hand or spray, to the wetted area you wish to clean.

Rub or scrub it into the surfaces, leave it to react with the dirt for a short time, and then pressure-wash it off.

Pressure washer detergent tank

Add your detergent to the tank, following the manufacturer’s instructions. Be sure to check up on your pressure washer terminology so you don’t put it in the wrong part of the machine.

A detergent tank is more popular in a petrol pressure washer

as they normally come built-in, although some electric pressure washers have them built in it’s slightly less popular.

It is best to use a lower pressure nozzle, spray as normal, and in a sweeping movement and the detergent will be applied.

As earlier, allow the detergent to work for around 5 – 10 minutes and blast off.

Don’t allow the detergent to dry on your surfaces especially during sunny days.

Feeder Hose

Some manufacturers provide a feeder pipe, from your machine, to connect to your detergent bottle to siphon into your tank.

 You will, of course, need to keep moving the detergent bottle around with you.

Always use appropriate, specially manufactured pressure washer detergents and follow instructions carefully. Your pressure manufacturer may recommend a brand but there are lots to choose from.

Always be sure that the pressure washer detergent you have chosen is appropriate for your surfaces. A solution aimed at cleaning decking or paving stones, for example, may not be suitable for cleaning your car. 

Never be tempted to add general, household cleaning detergent or laundry detergent directly into your pressure washer tank. Most importantly don’t ever add any form of bleach to your machine tank.

Internal damage might not be evident immediately, but as the bleach runs through your washer over time, parts may become eroded and serious damage will be caused.

Using such products may also render any warranty or maintenance schemes you may have bought with your washer, non-applicable.

You can, however, make your own simplistic and/or environmentally friendly pressure washer detergent.

Online recipes include ingredients such as vinegar, water, phosphate-free detergent, and other household products. You can also find recipes that are specially designed to tackle different kinds of dirt or stains on different surfaces.

Pressure Washer Detergent for Cars

A great use for pressure washer detergent is to use it to clean your car. You can use it directly with a hose or get a snow foam attachment. 

The snow foam attachment is great and will spread soap and detergent all over the area you are looking to clean.

Then you can use a sponge or other cleaning device to clean your car before switching back to a normal hose to finish off. 

karcher k2 compact electric pressure washer


Using detergent on a pressure washer is something that will make your life a lot easier when it comes to cleaning whatever you are cleaning. 

Be sure to clean out your hose by running clean water through it after you have used detergent to stop any leftover sitting in the tube and potentially causing damage.

Jeff Kirby
Jeff Kirby


Jeff is our head reviewer here at and has over 10 years in the commercial pressure washing business. What he doesn’t know about pressure washers isn’t worth knowing. 

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