Dear Dave,
Can I use a pressure washer to clean my RV? It seems a simple garden hose doesn’t get off the grime, and especially bird droppings and tree sap. —John, 2013 Forest River Wildwood
Dear John,
I do not advise using a pressure washer to clean your RV for many reasons. It is important to understand the dynamics of a pressure washer and the three factors that affect the cleaning efficiency.
Pressure per square inch
First, there is pressure per square inch (psi). Most people think that is the only thing to look for, i.e., the higher the pressure, the more force and cleaning power. Therefore, many RVers think that just getting a lower psi machine will be safe. Wrong.
Water flow rate
Just as important is the water flow rate. I ran a company called Easiwash that made a commercial pressure washer that was sold and installed mostly in fast serve restaurants, with Sonic being our biggest customer. It only had 2000 psi, but produced 3.6 gallons per minute, so it out-performed most 3600 psi units.
Nozzle
The final factor to consider is the nozzle, which comes with various orifice degrees and sizes. You will notice several colors that manufacturers use to quickly identify the nozzle for the best application.
The first two numbers of the model are the degree or angle of the spray, and the last are the size of the orifice. For example, a 15050 has a 15-degree fan and a .050 hole. Most of these are yellow for quick reference and gave a nice fan size at 2000 psi. The green nozzle was a 25100, which had a 25-degree fan and a .100 orifice. It was larger and only produced 400 psi. The red tip had a 0 degree fan and shot a laser beam that would rip apart concrete!
The smaller the orifice, the higher the pressure—similar to the pressure when your thumb is applied to the end of a garden hose.
What pressure washing can do to your rig
Don’t get me wrong, you can use a pressure washer and you will see many RV owners doing so. But you need to understand the critical areas that can cause moisture penetration or damage to materials. Even if you dial the pressure and flow down and use the right tip, you must be careful where you aim the stream.
Windows have a butyl tape between the frame and the sidewall and it can collect grit and dirt and looks bad. Aiming the stream directly at the butyl tape can cause moisture to penetrate into the sidewall and force the butyl tape to move and not effectively seal the joint.
If the window is a slider type, the joint between the two panes of glass has a simple felt-like tape that is not a solid seal, and pressurized water could blow into the rig. Even the tip-out type window has a light rubber seal around the perimeter that can be penetrated by a pressure stream.
Also, many RV windows have weep holes at the bottom of the frame to allow moisture to escape, but will also allow moisture to penetrate with a pressurized stream.
Decals
Decals—No, no, never, never, uh, uh, uh! Even though decals look solid and smooth on the sidewall of your rig, they are actually porous. Using any type of pressure can saturate them and cause damage. Plus, if the water gets under a crack in the material or a loose edge, it will lift the decal like a kite and ruin the material. Always wet the decal with low pressure (less than 60 psi) water and hand wash with mild detergent.
RV roofs
Manufacturers of soft RV roof material such as EPDM, TPO, and even the new PVC do not recommend using a pressure washer on their material. I have found EPDM to be the toughest to clean. It seems to have a “grain” or rough surface and gets more dirt, which eventually causes more mold and mildew… not to mention how bird droppings seem to cling to it!
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Dave, you are fully correct about the dangers of using a pressure washer on an RV. I’ll add one more, on aluminum sided RVs, never, ever, apply water pressure (even with a non-pressurized hose nozzle) upwards on panel joints. You can force water past the joint and it can then run down behind the lower panel.
All that said, I do use my pressure washer on my EPDM roof – with the attached sudzer. I put undiluted car wash in the canister and the attachment mixes the right amount of water with the soap and puts it on the roof with a safe pressure. I follow with a broom-style mop head on the suds and a clear water rinse. Finally a roof RV protector.
An electric pressure washer is standard equipment for auto detailers, so you absolutely can use one to clean an RV. However, how you use it is critical. While they produce extremely high pressure close to the nozzle, it drops dramatically with distance. You could seriously injure your hand if you put it into the stream at the nozzle, but it’s perfectly safe at ~18″
Always use a fan nozzle, 15 degree minimum. Don’t use the high pressure to blast away grime and stains! Use it from a distance to wet the surfaces before cleaning them with auto soap and a brush (for roofs) or a microfiber mop (painted surfaces and windows).You then use the pressure washer – again, from a distance – to rinse.
A pressure washer also allows you to use a “foam cannon” to apply soap to your RV or other vehicle, which is the ideal way to wash it.
I would avoid using a gasoline-powered pressure washer, as they typically produce much more pressure than necessary for washing a vehicle, increasing the likelihood of damage if you’re not careful.
Thank you for the discussion, Dave. We have a gas-powered pressure washer, but I rarely and only briefly considered using it to clean either RV. Instead, I use a foam gun attached to a garden hose (https://a.co/d/0a7mZkNw), ionized water (https://a.co/d/0fdZ9gUo), and brushes and wash mitts to clean the roof and exterior of our RV. I would be concerned about damaging the RV if I used a pressure washer. Have a great day and safe travels!