Dealers of homeowner machines like to refer to CUs when they show you a power washer. This number is the result of multiplying the PSI by the GPM. If you have 3000 PSI and 4 GPM, you have 12000 CUs. For homeowner machines, this is a good comparison of the power you are buying. For professionals, CUs have little meaning. GPM is most important, and PSI is less important, and the CU formula makes them both equal. The best solution is to talk to a dealer who really understands what you are trying to clean because he will steer you to the right GPM and PSI for the job.
Belt Drive vs Direct vs Gear Driven: The gasoline engines used for power washers all run at around 3450 RPM. In a Direct Drive power washer that pump is bolted to the engine shaft, so it spins at the same 3450 RPM. In a belt drive unit, the engine is tied to the pump through pulleys and a belt and the speed of the pump is reduced to either 1700 RPM or 1400 RPM. In a gear-driven machine, the engine delivers power to a transmission that in turn spins the pump at a reduced speed (1700 RPM).
Direct drive power washers transfer the vibration of the engine directly to the pump as well.
The faster pumps of direct-drive machines are spinning so fast that they cannot draw water from a tank or a lake very well. They tend to work fine when the water is forced into the machine (like when you hook it up to a hose from the house).
The slower moving pumps (belt driven or gear driven) work less and wear less, so they tend to last many years longer. They will also pull water to the machine from a tank, so your power washer shouldn’t ever be starved for water (a problem that results in destroying the pump).
Gear driven pumps still transmit the engine vibration to the pump because everything is hard-bolted together. However, the pump in a gear-driven model is running at a similar reduced speed to the belt- driven models. This kind of power washer has not become popular since it was introduced because there is obviously one more part to break in the system – the transmission.
Portable vs Stationary: Stationary power washers are used in car washes, factories, etc. They are installed in place and never move. Portable power washers are used by contractors who travel to the customer to do the work. There is a crossover model called a skid unit - a stationary machine designed to be installed on a trailer so that it can be taken to the customer’s site for the work. The most common machines for contractors to use are cold water portables (for small residential work) and hot water skid units (for large commercial work or high-volume residential work).
Wobble vs Axial vs Camshaft Pump: Since your pump is the heart of your system, it is critical to understand what you are buying. Every pump manufacturer makes several grades of pumps – Good, Better, and Best.
The Wobble design requires a piston to push against the pressure in the pump and the pressure of a spring. This is an inexpensive design to build, but it is relatively inefficient, too. This is the design found on most homeowner machines. It is designed to work for limited hours at a time and very limited hours per year, which is OK for a homeowner but doubtful for a contractor who wants to work every day. Wobble pumps tend to last for around 300 hours before needing extensive service or replacement.
The Axial design is similar to the wobble design with a couple of important differences. Most axial pumps have larger oil reservoirs and bearings, which allow them to be used for longer periods of time and more hours per year. They still are inefficient (like the wobble) but several lower-priced contractor-grade machines work fine with the axial design. Axial pumps tend to last for about 600 hours before needing service.
The Camshaft design delivers the most power and durability of all these designs. It uses connecting rods on a cam with large bearings like a car engine, so it runs cooler and lasts longer. It is able to hold up to continuous use for hours and hours as long as it is kept cool. Cam pumps tend to run for 1000 hours before needing service, and tend to last 2000 hours before needing extensive service or replacement.
Heavyweight vs Lightweight: If you are buying a portable power washer, it makes sense to pay attention to the weight of the unit. After all, you are the one who is going to lug it all around and move it into and out of your truck. Aluminum frames can be fragile, and steel frames can be heavy, so talk to your dealer about how you are going to transport the machine. He may be able to steer you to a good solution for your needs.
Home Model vs Contractor Model: The final choice for you to think about is durability. We have already discussed the difference in pumps, even from the same pump manufacturer. The cheapest power washers usually have the cheapest pump, which won’t hold up well for most contractors. There are other considerations that you need to think about, too.
The finish of the machine can be very important. Powder coating holds up better and lasts longer than painted frames. Steel frames rust. Aluminum or stainless doesn’t. Aluminum can be bent, steel is very rigid. Choices, choices.
For power washers that will be used at least 20 hours per week and sometimes up to 8 hours in a day, the lower priced machines just won’t last very long. They come with inadequate parts throughout, such as the unloaders, pumps, and even the engines. Just because it says “Honda”, for example, doesn’t mean that all Hondas are the same. This is where Grandpa’s “you get what you pay for” saying really is true.
By the way, everybody loves Honda engines. They hold up very well. Vanguard engines are built every bit as well and last as long as Hondas, and seem to deliver more real power per rated horsepower. That means I measure a little more "ooomph" from a 16 HP Vanguard than I get from a 16 HP Honda.
There are a lot of different pump brands to choose from out there, too. If someone states a preference when buying a new pressure washer, Cat is the most specified brand I hear. My experience is that all of the major brand pumps are excellent, and I get the most serviceable use per dollar from General Pump and AR. Other folks may have other experiences, but we specify General Pumps for the machines we bring into stock.
So, getting back to discussing value, if you buy a $900 power washer and you get six months use out of it, that purchase cost you $150 per month. If you bought a name brand commercial- grade machine of the same specifications for $1600 and you got 5 years of use from it, that purchase cost you $27 per month. Which one is less expensive?
Let me relate some of my own experiences. As a pressure washer dealer, I see homeowners dragging in dead machines that are only a few months old every week. These machines cost more to fix than to replace, so my ‘boneyard’ is full of discarded homeowner units.
I recently sold two old pressure washers that I used when I was a contractor and didn’t want any more. They were each 12 years old and each ran like a top. One had needed only routine maintenance over its life. The other had to have the pump completely rebuilt about three years ago. They were both belt- driven units with AR pumps and Honda engines. I paid about $1500 for each and sold them for about $300 each. When I added up all of the maintenance costs and the purchase price and then subtracted what I got for them when I sold them, those power washers costs me about $16 per month to own. Is there a better deal than that anywhere?
If the bottom line for you is how much cash you have to fork over right now, consider an alternative. A reputable dealer can get you into a quality power washer on a lease or finance contract. In the long run, you are better off with the better equipment. You will spend less of your cash today and less over the life of the machine – even with the lease or loan interest added on.
Written by Pete Marentay from
Sun Brite Supply
