The Ultimate Guide To Choosing The Right Pressure Washing Detergent

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If you’re a seasoned pressure washer veteran, then it’s quite likely that you’ve had to get yourself a black 65-degree soap nozzle, or a pressure washer with an onboard detergent tank, to tear apart those tough stains.

If you’re just a casual pressure washing recruit, you probably haven’t used either of them. And that’s fine, because most of the time, high-pressure water alone gets the job done.

But there’s always a bigger fish, and sooner or later, you’ll run into a stain that water alone can’t shift. That’s when the black tip, the soap tank, and pressure washer detergent comes in. This article is going to give you an overview of how you can use detergents in pressure washing, and some practical advice while doing so.

The Basics of Detergents

Let’s start at the very basics.  Simply put a detergent is a substance used for cleaning. It uses surfactants to remove dirt, stains, and other unsavory substances. Detergents may come in powder or liquid form.

Surfactants have two ends. The head prefers to stay in water, while the tail end sticks very well to oil and oily substances. When the surfactants get close to oil, the tails dip in and stick into the oil. As more surfactants are attracted to the oil, the heads form a barrier that stops the oil drops from merging with other oil drops, breaking them up. When you couple that effect with flowing water, oil gets carried away, no longer sticking to the surface it used to be on. To put all this in layman's terms—detergent breaks up grime at a chemical level.

The combination of detergent and water is important because water by itself flows well enough, but doesn't necessarily take all the grime with it. Detergents can take dirt and grease with them, but there’s not enough flow to carry them off. Put the two together, and you have the perfect combination to remove all the built-up grime and stains.

A usage note: While we use the words ‘soap’ and ‘detergent’ interchangeably, soap is more accurately one kind of detergent. Soap is generally solid and is largely made from natural ingredients, while most other products labeled as detergents use chemicals and other synthetics. In this article, we’ll also say ‘cleaning solution’, which means the same thing as ‘detergent’.

What Kind Of Detergents Are There?

Take a look around the detergent section of a pressure washer manufacturer’s website, or look at what Lowe’s or Home Depot has to offer, and you’ll find a wide selection of cleaning solutions for sale. You’ll see a whole list of stuff for vehicles, a section for houses, degreasers, and so on. So, if you’ve got a pressure washer, where do you start?

For the most part, you can get by with general purpose cleaner. As you can expect, that’s a solution for dealing with most stains and grime you can expect to encounter without being too harsh. It won’t work as well as a solution for that specific application, but if you don’t expect too much work on that particular surface or if you've got a lot to clean and don’t have time to switch out specialized detergents, it’ll serve you fine.

Degreasers are formulated to remove caked-on oil and grease stains. They see the most use on tough floors, especially the floors of restaurants and automotive shops. Some degreasers will also work well on equipment and vehicles, especially built-up road film; they’ll generally see effective use on heavy equipment or the insides of engines.

Vehicle detergents could be a category all to themselves. Boat detergents, for instance, need to deal with saltwater and algae deposits, while car detergents go for road film, salts, the usual dirt, and so on. Be careful not to get them mixed up if you’re dealing with multiple types of vehicles, because the heavy-duty caustic detergents for heavy equipment will mess up aluminum and paint and leave your poor car looking mighty sad. Some car detergents even have wax built in, to keep your car looking shiny.

House cleaning detergents attack ingrained dirt from siding but are formulated to avoid damage and color fading. Near them, you’ll also see deck and fence detergent, more geared to those specifically. These solutions are generally not as harsh as degreasers and vehicle solutions, as residential cleaning generally sees a lot more wood and similar material instead of heavy-gauge steel. Some cleaning solutions are specifically geared for a particular material, so you may find detergents for vinyl or brick.

A note with specialized solutions: Read the warning labels, and they’ll tell you what you should not use them on. We all know pressure washers can damage the items or surfaces we’re cleaning if improperly used; the same goes for detergents. Furthermore, never use bleach in your pressure washer; it’s too harsh for most applications, it’ll hurt the surroundings, and it’ll damage your washer.

This is just a basic overview of what’s available, and there are a lot of different formulations available on the market for different needs. You’ll generally see detergent being sold by the gallon, and that’s fine for residential use, but if you’re a contractor and see yourself using a lot of detergents, you can generally find concentrates in bulk form, and perform the mixing in-house.

Practical Application: Soaping Things Up

Once you've got your cleaning solution in hand, you now face the practical question: How do I spray detergent on to a surface? That depends on what kind of washer you have, and what arrangements its maker came up with for soaping. Of course, you’ll need your 65-degree detergent nozzle.

If your washer has an onboard detergent tank, then it’s simple enough; just pour your cleaning solution into the tank and flick the valve to the on position when you’re ready to soap up. Switch in your soap nozzle, and apply detergent using your wand.

If your pressure washer doesn't have a built-in detergent tank, then it very likely has a vacuum siphon tube. In that case, bring out your detergent bottle, or put the solution into a convenient jug or bucket, bring it over to your washer, and stick the siphon into your bucket and you’re in business.

There are also foam nozzles with screw-in bottles that attach to the end of your wand. These attach the same way as a typical soap nozzle, so just stick it on and get to soaping. These may run low on extended jobs, though, so make sure refills are handy.

Now, depending on the surface, you may want to pre-treat it before putting the soap on, especially if you’re dealing with old, beat-up concrete. Treat the trouble spots and give the area a good soak with the hose before you get started.

After the preliminaries, that’s when the soap comes in. A few tips for effective soaping: Start from below and work your way up to help prevent streaking. Remember to overlap your applications, as you don’t want to miss something and come back to it later. Let the solution sit for maybe five to ten minutes, but don’t let it dry out. Check the weather and keep an eye on what you’re cleaning. If it’s hot or sunny out, you may need to reapply every so often so it doesn't dry.

Once the detergent has done its magic, it’s time to rinse. Switch off your tank valve, or remove the siphon from the bucket, or take off the foam nozzle. Remember to give your wand a few squirts to flush the remaining detergent, then switch in a nozzle appropriate to the job at hand. After that, rinse off the detergent, doing so from top to bottom.

Environmental Repercussions

We know to exercise caution when using pressure washers and detergents, but the danger doesn't stop there. The harsher cleaning solutions can already do pretty gnarly things to wood or aluminum; what more can they do to the environment?

Be very careful with your detergent use, and make sure to check composition thoroughly. The EPA gets really irritable about violations of the Clean Water Act and can slap down heavy fines if you’re not careful about wastewater discharge. Safe discharge and compliance with the Clean Water Act can take up a whole article unto itself, so we won’t get into that now, but it’s important to be aware of that potential legal wrinkle if you’re using detergents in your pressure washing.

If you’re using chemicals, discharge into a sanitary sewer. Most storm drains go out into a body of water without any treatment, so discharging into a storm drain is effectively discharging into a federal watercourse, which will get the EPA on your case. A sanitary sewer passes through a treatment plant. Check with your client and with the city to be absolutely sure of discharge methods.


Detergents are a powerful tool in your array of cleaning implements. You can take on even the most unsightly and the long-lasting stains with the right cleaning solution at your side. Coupled with the sheer power of a pressure washer, nothing is ever too much for you to clean out. Whether you’re dealing with houses, bulldozers, cars, or a greasy shop floor, there’s a solution for every situation. And if in doubt, just bring out the all-purpose cleaner.

Richard Allen