I want to dispel a common myth about those great time-saving tools - surface cleaners. Some people believe that a 24? or 28? surface cleaner can get the job done faster than a 21? surface cleaner. This urban legend breaks down under examination, however. Let me explain.
The deciding factor about efficiency in surface cleaners is a mathematical function of the number of nozzles, the area covered (diameter), and the speed of rotation. When it comes to 2-arm surface cleaners, the truth is that the larger the surface cleaner, the slower you actually have to move it around to clean the surface without leaving stripes. The cleaning power is truly in your GPM, not the diameter of the tool.
If you compare 2-arm (two nozzle) surface cleaners driven by the same pressure washer ? with properly sized nozzles ? you find that they clean at approximately the same speed no matter what the diameter. Think of it this way; if you have a 21? and a 100? surface cleaner and each are fed by similar 6 GPM pressure washers, you will have to move the 100? surface cleaner extremely slowly - and you will end up cleaning the surface in the same amount of time.
The only way to change (speed up) the 100? surface cleaner is to add more nozzles (again, properly sized) or find a way to increase the speed of rotation (motor-driven?). With more nozzles, you will be able to move the 100? surface cleaner faster.
This advantage begins to disappear if you divide the flow you have by too many nozzles. Without getting overly scientific about it, my theory is that you should not drop much below 1.5 gallons per nozzle and are most efficient closer to 2 gallons per nozzle. That means you should not go for more than two nozzles until you have at least a 5 GPM pressure washer. It also means that a 2-nozzle surface cleaner is all you need to pay for unless you have at least 6 GPM available.
I keep talking about properly sized nozzles. Some surface cleaners come with nozzles and some don?t. I actually think it is better to select your nozzles separately because that way you will be sure to get the proper ones. Some of the surface cleaners we sell do not come with nozzles, which is a blessing in disguise. When you are sizing nozzles for your new surface cleaner, the key is simply to divide your flow (GPM) by the number of nozzles and then go to the Nozzle Chart to find the right nozzle.
Sometimes this creates a math problem for the contractor. If you own a 5.5 GPM pressure washer and purchase a 2-arm surface cleaner, you have to divide 5.5 by 2 (resulting in flow at each nozzle of 2.75 GPM). With that same pressure washer and a 3-arm surface cleaner, you end up with 1.833 GPM per nozzle (5.5 divided by 3). No nozzle chart breaks down that finely. The easy answer is to round up or down to the closest whole number and select your nozzle that way.
There is, of course, a complicated mathematical formula that you could use to find the absolute right nozzle size. There is little value in using that formula, however, since manufacturers only make typical standard sizes of nozzle orifices. I did find out recently in a discussion with Larry Hinckley at Rahsco that GP makes some custom nozzle sizes available to manufacturers and dealers. If your surface cleaner is not performing the way it should, it is more likely that you have nozzles that aren?t sized properly than any other problem.
We see this all the time in our repair shop. It happens most frequently when someone buys their surface cleaner either from a dealer who doesn?t understand the nozzles or from a Craigslist ad. If you aren?t happy with how your surface cleaner performs, flip it over and check the nozzles. Be willing to experiment with different nozzles until it works the way you expect it to.
While on this topic, let?s look at surface cleaner design. A popular 28? surface cleaner design has a fixed axle and a front caster layout. With that design, you are forced to move the surface cleaner from back to front and then front to back (much like you move a vacuum cleaner). In that motion, you are forced to cover much of the area you are cleaning twice. This can be a bit cumbersome and at best is an inefficient, unnatural motion. If you have a ?floater? design or a four-caster design, you can move the surface cleaner from side to side easily, which is a much more natural motion for your arms. This natural motion makes using this kind of tool naturally faster that using a fixed-axle design.
We still offer the fixed-axle design because a lot of people like it and are used to it. If you ask us for an opinion before you buy, however, we will always steer you towards a floater or a free caster design. We want to help you get done with the job faster.
The last word: Use an inline filter on any surface cleaner. Most cities allow an large amount of particulate matter in the water supply (usually a filler in their chlorine mix that doesn't fully melt). This particulate can affect your swivel and/or your nozzles. A partially (or fully) blocked nozzle will give you awful results. A filter is usually less than $10 and can save you a lot of time and money maintaining your equipment.