Post-season harvest is a great time to get things cleaned up, serviced and put away. While it is satisfying to see a clean and shiny piece of equipment, I must say, as I get older and acquire more machinery to wash, the motivation to clean up is far less than it once was.

Overbay andy
Extension Agent / Virginia Cooperative Extension
Andy Overbay holds a Ph.D. in ag education and has 40-plus years of dairy and farming experience.

This is where a pressure washer can really be a blessing. A good pressure washer is worth its weight in gold if matched up to the task and used correctly. A pressure washer is just about a necessity on many farming operations and, with the cost of equipment these days, it pays to keep machinery looking good.

However, not all pressure washers are created equal, and mismatching a pressure washer to the incorrect job or setting can yield anything from unfavorable results to costly damage.

Understand the rating

First of all, you need to know your numbers. Most novice pressure washer buyers are enticed into a purchase looking only at the pressure rating (PSI) of the washer in question. Experienced owner-operators will tell you while PSI rating is important, the pressure behind a pressure washer is the amount of water (expressed as gallons per minute or GPM) they can put out at that pressure.

The PSI rating of a washer gives a representation of how much stripping pressure a machine offers, while the GPM rating represents the ability of the machine to rinse the dirt and grime stripped and out of the way.


For example, pressure washer “A” has a rating of 1,500 PSI at 4 GPM; pressure washer “B” has a rating of 2,000 PSI at 3 GPM. For each machine, the cleaning unit rating (PSI x GPM) is 6,000 cleaning units.

So they are equal, right? No, they are not. Washer A has a greater ability to get stripped grime out of the way, so it will do the same job faster than B, even though washer B has a higher pressure rating.

Increasing the volume of water striking the surface of the equipment you are cleaning necessarily increases the weight of the water being applied, and that weight makes all the difference. Think about it this way: If you get hit by a baseball traveling at 60 mph, it hurts. If you get hit by a semi-truck going 60 mph, the results are far more devastating.

A good friend recently purchased an inexpensive washer at a local supply store rated at 1,600 PSI and 1.2 GPM. In comparison, my farm washer is rated at 3,500 PSI and 4 GPM. If we convert each washer over to cleaning units, the difference in the washers is stark: 1,920 cleaning units to 14,000 cleaning units. My washer is over seven times more powerful, but that isn’t necessarily a good thing.

My friend uses his washer to do the occasional odd job – washing off his deck, cleaning siding on his house or washing his car. While my washer is more powerful, used indiscriminately on my friend’s chores, the results would be ruinous.


This leads us to some do’s and don’ts of safely operating a pressure washer. Let’s begin with the do’s: Begin by reading your operator manual. Keep all shields and guards in place and securely fastened. Check the oil level in your pump and motor (if applicable) every time.

Wear the proper personal protection. Protect your eyes, face, hands and feet especially. Check the surface you are standing on, and keep an eye out for slippery conditions. Test the surface being cleaned by washing a small area first.

Use only nozzles and attachments recommended for your washer, and wash the surface thoroughly to prevent cleaning agents and chemicals from being left behind.


As for the don’ts: Never add fuel to a hot or running washer. Don’t leave the nozzle in the closed position for more than a minute or so, as the pump may overheat. Never repair a leak while the washer is running, and never point the washer at a person or animal, as many washers are powerful enough to injure terribly.

Don’t hold the nozzle too close or too long on a surface. Significant damage can occur to even the strongest surfaces. (Remember, water on a rock eventually made the Grand Canyon.) Never use your washer while standing on a ladder, as you need to keep both hands on the wand, especially when the nozzle is first engaged.


While pressure washers are handy little critters, not everything needs a pressure washer pointed at it, regardless of the cleaning unit rating. One of the first things that comes to mind is the inside of your tractor cab. Now I have seen cabs that could stand a good cleaning, but introducing water into the modern cab and all of the electronic connections within is asking for trouble.

In fact, I don’t even use a water hose around a tractor cab. I use an air hose and blow the cab out, and use a vacuum to hold dust in check as much as possible. Even a little water in the wrong place can lead to corroded wiring and connections, turning your tractor into a multi-ton paperweight.

While electronic failures are frustrating, using a pressure washer around home and farm electrical wiring and circuits can be fatal. Think of your pressure washer in much the same fashion as your high-powered rifle. Make sure of your background before you ever pull the trigger.

Be safe, and happy cleaning. end mark

Andy Overbay holds a Ph.D. in ag education and has more than 40 years of hands-on dairy and farming experience.

Andy Overbay