How To Pressure Wash Your Car - The Detailing Nerd’s Guide

Are you tired of hauling buckets of water and soap to wash your car? Do you finally feel guilty about all the water you’re dumping out of the garden hose with every car wash?

It’s time to step up your detailing game and get yourself a pressure washer. If you’re in the market for one, we’ve caught you at just the right time. In this article, we’ll take an in-depth look into pressure washers, what you need to look out for when buying, and how to properly use one for premium car cleaning.

Let’s get started.

Your Garden Hose is Not Good Enough

We know you’ll ask, so no, a garden hose is not efficient for a decent car wash. Most garden hoses chug out 7-15 gallons per minute at 10-40 PSI. This is way too much wasted water, even if you live in a water-rich state. It’s also not the right pressure needed for blasting away hardened dirt, baked-on bird droppings, and other contamination found on your car.

When it comes to car washing, it’s fine to use a garden hose if the car’s not too dirty. Although at least be considerate about our resources and put a water-saving nozzle on to use less water, which will also increase the pressure slightly.

Anatomy of a Pressure Water Work?

The pressure washer has two major components you’d want to associate yourself with - the motor and the pump.

The Motor

Pressure washers always have some type of motor to provide the power for the pump. It can be an electric motor that plugs in a regular power outlet, or a small gasoline/diesel combustion engine, like the one you’ve got in your weed wacker or chainsaw.

We’ll talk about the differences between the two in a minute, but just keep in mind the power and efficiency of the motor are critical to the overall performance of the power washer.

The Pump

Pressure washers commonly use one of three types of reciprocating mechanical pumps:

• Wobble Plate Pump - Basic design found in most consumer-grade power washers. Only good for “low” pressure and flow rate applications, but typically all you ever need for washing your car.
• Axial Cam (Swash Plate) Pump - More efficient and sophisticated design compared to the wobble plate. Found in some upscale consumer-grade and commercial power washers.
• Triplex Piston-Crankshaft Pump - Similar construction to the rotating assembly of your engine. Typically found in high pressure and high flow rate applications, stripping paint, and other coatings from metals and concrete. Very expensive and only found in professional and industrial power washers.

Regardless of the exact mechanism, all reciprocating pumps feature a plunger or piston. These pumps make back-and-forth strokes to draw water from an inlet valve and then shoot it under pressure through an outlet valve. The inlet is connected to a water tap or a reservoir, and the outlet is connected to the gun. Both valves work in a single direction, so water only goes one way.

The Gun

The spray gun itself is just an ergonomic handle with a valve connected to the trigger. When you press the trigger, the valve opens and allows high-pressure water to blast out into the extension wand and the nozzle.

The Nozzle

The nozzle has an orifice, whose size and design dictate the velocity, shape, and flow rate of the water jet. Choosing the correct spray nozzles for your application is of critical importance.

Here’s a common misconception about pressure washers. You’re not hitting the surface with high-pressure water. As the stream of water shoots out of the orifice, it transitions from high pressure to atmospheric pressure almost instantly, and in doing so, gains an inversely proportional impulse that accelerates it forward. Upon splashing onto the surface, this fast-moving water transfers its kinetic energy to the dirt and soap already on the surface area and blasts it off.

Key Properties Of Pressure Washers

Different pressure washers come with different performances. So what’s right for your needs? Here are the parameters you need to watch out for when choosing your first (or last) pressure washer.

Pressure

As you might already know, the main parameter of a pressure washer is the water pressure as measured at the outlet valve. Typically, detailing professionals recommend not using over 1500 PSI (pounds per square inch) when washing your vehicle. You need even less to wash any wooden decking you have around the house. If you want to clean a concrete driveway or strip the paint from a metal fence, you’re looking for a minimum of 2,500 to 3,000 PSI.

The vast majority of pressure washers will be more than adequate for washing your car, but if you also want to do some work around the house, perhaps clean farming equipment, you’ll need more oomph.

Flow rate

Flow rate is measured in gallons per minute or GPM. GPM doesn’t influence the strength of your power washer - just the speed at which you’re getting things done. The more you have, the better.

Typically, consumer-grade power washers will give you about 1.5-3 GPM.

Water temperature (inlet)

Some pressure washers can run with hot water, increasing the cleaning strength of the jet. Water temperature is irrelevant for detailing but can be a deciding factor if you're also planning to clean patios and other bits around the garden.

Weight

Light is right. You don’t want to be carrying around a 20-30 lb machine if you can avoid it. That said, too light also means there are probably plastic components in the motor and pump, which can break more easily.

It’s not necessarily true, but generally, the heavier power washers with equal characteristics will tend to have stronger internal metals and last longer.

Types of Pressure Washers

Pressure washers separate into two main categories depending on their power source.

Electric Pressure Washers

Electric pressure washers are powered by an electric motor that drives the pump. These washers are weaker compared to gas-powered machines, typically producing between 1,000 and 1,800 PSI and 1.8 - 2.5 GPM.

This is more than enough water pressure to clean any car, though if you have a lot of them lined up for washing, you might wish for more flow rate.

A few benefits to the electric power washer are its compact packaging, reduced weight, and noise in comparison to a gas-powered one. Electric power washers are perfect for the driveway warrior who details their car religiously and washes the patio once a year.

Some top brands to look out for are Karcher, Nilfisk, and Kranzle.

Gasoline / Diesel pressure washers

Gas-powered washers are heavy, loud, smelly, and require some general knowledge about engine maintenance. However, they are your go-to choice when you’re looking for a turbo pressure washer that gives you high pressure, high flow rate, and ultimate performance.

You need to be careful using this one and always double-check your settings. Gas pressure washers can easily go too hard on the paint and rip off badges and decals from the body.

One benefit of gas pressure washers is they can work in remote areas, whereas you need a power outlet to run an electric pressure washer. If you have to haul a generator as well, you might as well get a gas power washer with a gallon of fuel, and a water tank. Another benefit is they generally last a lot longer when properly maintained.

Pressure Washer Accessories

Most pressure washers will come with a basic kit, containing fittings, pressure hoses, a gun, extension wand, soap tank, and several nozzles.

These are typically fine for the majority of your home needs and will work especially well for a car wash. But if you start pressure washing a lot, or you’re a professional detailer, you’ll find yourself quickly annoyed by low-quality accessories.

The Right Gun Will Make Your Life Easier

Many of the cheap guns start to leak out after six months of regular use. Depending on the quality of the seals, you might be looking at wet pants every time you wash your car - not fun.

The better quality ones come with a swivel fitting that allows them to rotate without twisting the hose. You will be immensely impressed by how much easier it is to wash anything without having to fight with the hose, constantly fidgeting around to untangle it.

Foam Cannon

The foam cannon is an attachment for your car pressure washer that includes a detergent tank. It mixes soap, water, and air and shoots a thick layer of foam on the body panels. The suds are super fun to play with and stick to the surface longer, allowing you to scrub the body without having to reapply more than you need it. A foam cannon allows you to wash a lightly dusty car without ever touching it, though you still need to scrub to get harder dirt and muck out.

If you have the pressure washer already, it’s pointless to still use a bucket of soapy water to wash the vehicle.

Hose Reels Cut Back the Hassle

You don’t really need a hose reel, but you’ll appreciate how much quicker and easier it is to put your pressure water away after cleaning the car.

Quick Connectors

The best pressure washers come with a quick-connect system, but make sure the one you’ve picked has them. The quick connectors allow you to attach and swap different components like hoses, guns, wands, nozzles, and foam cannons in a snap.

Some pressure washers come with an M22 or a ⅜-inch threaded connector. These will work just fine but are a hassle to screw and unscrew if you need to change components several times throughout your washing.

Pressure Gauge

A pressure gauge is recommended on higher-powered pressure washers, so you can make sure you’re getting the right pressure and not causing any trouble.

The more upscale models already come with a pressure gauge, but if you’re buying a cheaper gas-powered one, it’s a sound decision to get one.

How To Pressure Wash Your Car

Okay, you’ve tricked out your pressure washer, so now it’s time to put it to work. It’s not rocket science, but there are a couple of things you want to watch out for.

Choosing The Right Nozzle

As we already mentioned, the orifice of the nozzle can vary the pressure and flow rate of the power washer, as well as changing the shape of the stream.

Each washer varies in terms of accessories but should come with one adjustable nozzle and a knob that controls the shape of the orifice. More commonly, power washers come with a kit of color-coded degree nozzles that have angles between 0 and 60 degrees.

The smaller the orifice angle, the more focused and stronger the water jet will be.

A 0-degree orifice will focus all the energy of the water into a single spot. That’s far too much force for washing the surface of your car and more suitable for stripping away paint or baked-on grime from the driveway.

For pressure washing the paint safely, use a 40-degree nozzle. It will give you a wider jet that spreads out the flow of water over every square inch of the car and thus reduces the impact on the paint. Certainly, don’t go any lower than 25 degrees, or you risk damaging your paint.

Dial-in Your Settings

Next, dial in the pressure and water flow rate for your power washer. Make sure you stay below 1,500 PSI and run as much GPM as you want.

Ensure your connectors are properly secured and always test the jet away from the vehicle in case something is loose and blasts off.

Depending on your spray nozzles and the pressure you dialed in, you want to keep the tip a considerable distance from the surface of the vehicle. The closer you get it in, the more energy you’ll focus on a smaller area. Start 2-3 feet away and move closer, but not any closer than 1 foot.

Pre-rinse

Pre-rinse the vehicle with a low-pressure jet. Don’t use the maximum pressure, because you may break off pieces of hard dirt and send them flying across the body before they have a chance to soften and dissolve. Unknowingly, this can create new scratches on the surface.

For severely muddy trucks and SUVs, consider pre-foaming the entire vehicle to soften and weaken the dirt.

Foam up the Vehicle

You know what to do, snap on your foam cannon with your detergent tank in tow, and carpet the body in soapy thick foam. Give it a minute to absorb and do its work.

Scrub With a Wash Mitt or Sponge

With the car soaped up, grab a clean microfiber wash mitt or sponge, dunk it in water and start lightly scrubbing the body. Go in straight-line motions to reduce the amount of swirl marks you produce in the finish. Make sure the suds don’t dry on the surface. If you have to, spray it regularly with water to keep it wet and active.

Rinse-Off

Kick your pressure washer into high gear and blast away all the soap and foam. Start from the wheels, so you’re not rinsing the worst grime back on the clean body panels, and don’t forget to dry the car off correctly as your final step.

Bonus: Careful! This video will make you buy a pressure washer!

Pressure washers are fun and badass. Is that a secret? They work a treat for around-the-home projects, but more importantly, they wash our rides. The above video shows some ultra-satisfying pressure washing clips.

Summary

Okay, this has been a pretty comprehensive tour around the subject of power washers. They really are the best tool for washing your car quickly and effectively, and also come in handy for many other tasks around the house.

These machines are great to have in your stockpile of DIY tools, and should you wish, you’re probably fine with a cheaper, smaller electric pressure washer from the likes of Karcher or even name-brand superstores. Also, an added bonus is most pressure washers come with a money-back warranty.