Finally the homeowner can learn the little tricks of the cleaning trade that the professional power washing contractors have been using for years to make their work look better, go faster and be more cost efficient.
The application of chemicals is one of the longest standing controversies in the power washing industry. There are just as many opinions on the correct method of doing so as there are chemical applicators. The one thing most contractors seem to agree on is that no single method will serve all circumstances efficiently. Of all the different methods, the three most often used are 1) down stream injection [after the pump], 2) chemical before the pump [through the pump], 3) and the chemical applicator pumps.
Each of these methods has their benefits as well as their limitations. Down stream chemical injection is most often used on cold pressure washers because of low cost and the ability to turn the chemical on and off at the wand. Chemical injection before the pump is most often used on hot pressure washers because of the ability to apply chemicals with hot water, which makes them more effective. And chemical application pumps are used where the chemicals are not compatible with the pressure washer.
The down stream injector is the most common to the power wash industry. They are coupled in-line and operate on waterpower. The water velocity is what creates the needed vacuum (venturi) to draw the chemical and mix it with the water flow. Changing the size of the discharge orifice regulates the water velocity. This is most often accomplished using a roll over valve, a double nozzle head (see page 4), or a dual lance wand (see page 12). Most manufacturers of these injectors claim that their draw rates are from 10% to 20%. With a few exceptions, I have found this accurate. The problem with this is that many people are requesting a draw rate in excess of 50%, which is only available with an injector that is especially designed to fit at the end of a spray lance (see page 13). The problems with this injector are cost and due to the location, it's a cumbersome package to handle for some applications. The contractors who most commonly request higher draw rates are ones who are applying chlorine to exterior surfaces such as buildings, decks, and fences. The reason for their concern is that the strongest concentrate of sodium hypochlorite (chlorine) available is 15%. When this is mixed at a 10% to 20% ratio in the injector, many people feel that it is too weak to adequately clean and remove mildew. From this springs another question, the advisability of using chlorine as a cleaning agent to begin with. We could pursue this to infinity and never reach a consensus.
Another problem with this type of injector is due to the restriction created in the ¼" pressure hose that is used as an integral part of a telescoping wand. A down stream injector will not work in most cases with a ¼" pressure hose. This is because the ¼" hose creates too much restriction and reduces the water flow (increases the back pressure) causing the injector not to work.
Other things that can inhibit the flow of water, thereby decreasing velocity and stopping the vacuum that is required to draw chemical, are: 1) discharge hose in lengths of 200 feet or more, 2) installing the injector before the hose reel, water heater, or other restrictive devices, 3) and using certain types of trigger guns that are too restrictive.
One advantage of downstream injection is that you will use less chemical. On the downside you will clean slower because you will be applying the chemical under low pressure and rinsing on high pressure. With up stream injection {before the pump} you will apply your soap as you are washing on high pressure and rinse on high pressure as well. You will use more chemical this way but you will clean faster and more thoroughly. Also down stream injector allows the operator to turn the chemical draw on and off from the gun whereas upstream chemical injection [before the pump] requires that the operator return to the machine to turn the chemical on and off. As you can see down stream chemical injection can save many steps and a lot of time over the course of a day. Another major benefit down stream chemical application over before the pump injection is that you can use chemicals that are corrosive in nature (like acids) because they never enter the pump, unloader valve, or heater coils.
Upstream chemical injection is done by restricting the inlet water to the pump. High-pressure pumps used on hot high-pressure washers can pull a vacuum. Therefore, these pumps do not have to be pressure fed and they have the ability to draw water and chemicals from water tanks and chemical tanks. The vacuum is created with a restrictor barb or gate valves in the inlet plumbing to the pump. The operator has to return to the pressure washer to turn the chemical on and off with a metering valve. These units have the advantage in any strength of chemical can be mixed with the inlet water. However, the chemical (usually a heavy duty alkaline detergent) must be compatible with the components in a pressure washer. Most quality high-pressure washer detergents are compatible with the internal parts of a pressure washer (example: R-109 or DNB-1430.
When considering the selection of injectors it is important for you to understand how they work and to determine their value to your style of cleaning. It is a well-established fact that chemical is cheaper than labor and that the best way to assure return business is to do the best job that we can.
The two types of chemical applicator pumps that are most commonly used in the mobile power wash industry are compressed air sprayers {pump up style} and electrical diaphragm pumps. Pump up sprayers are often used because of budgetary reasons. The mobile power wash industry is probably one of the least expensive fields of endeavor in which you can start and successfully run a business. Therefore, you will find many people searching for cheap answers to expensive problems. Mobile power wash contractors are on the whole some of the most inventive people that you will ever meet. Pump up sprayers are an inexpensive answer to an expensive problem that they face regularly.
There are different styles and makes of these sprayers ranging in price from $ 14.00 to $ 145.00. The lower priced sprayers being the kind that you would find in a garden shop or hardware store that are designed for homeowner use. The more expensive sprayers are of the type that you might find at a contractor supply or a pressure washer distributor. Some of the differences would be better stronger construction, viton seals and diaphragms, stainless steel corrosion resistant tanks or wetted parts and epoxy coated steel. You will find all makes and models in use in the industry but most often you will find the medium priced sprayers being used because they offer some longevity without the extreme expense. Some people won't use any other type of sprayer because they really prefer this method, but generally, they have chosen this method for economic reasons. Pumps up sprayers are available for spraying everything from acid to deck sealer. Although repair parts are available for these types of sprayers in many cases they are not worth rebuilding, depending upon the initial cost of the sprayer. When nothing else fits your budget, they can be quite useful. I have used these types of sprayers and for small jobs they are tough to beat. You can be in and out in less time than it takes to clean up a larger more sophisticated unit.
The electrical pumps most often used are self-priming, positive displacement pumps driven by permanent magnet motors. They utilize a heavy-duty ball bearing/offset cam assembly, which drives a reciprocating two-piston plate. A diaphragm is clamped between the inner and outer pistons sealing the pumping chamber and when actuated creates an alternating suction and pressure condition that opens and closes the inlet and outlet check valves. They will have either an internal bypass system or an on demand system. These pumps are available in 12 volt DC and 120 volt AC and 240 volt AC powered models. The diaphragm that should be used for corrosive materials is made of viton because it is the most resistant to the type of chemicals used in the mobile power wash industry. You will also need to use a valve assembly with viton parts. This will be incorporated in the new pump that you purchase when you specify the use is for corrosives. These pumps are available in different output volumes {expressed in gallons per minute}. These volumes will range from ½ to 6 gallons per minute. The size that one would choose would be directly related to the type of work that he is doing. Obviously if you were applying aluminum brightner to a truck you would not want to use a 5 gpm pump. Nor would you want to use a ½ gpm pump to apply deck brightner when preparing it to be sealed.
In choosing, the appropriate pump for your specific needs some of the things that you should consider is: the availability of electricity, the type of electricity available and the kind of chemicals to be applied. One of the more popular pumps used in the industry is the 12 volt model. This is because even if you don’t have a heavy duty charging system on your pressure washer and a large storage battery you probably do have some sort of vehicle with a 12-volt charging system that you can attach it to. This means that you can be totally self reliant without the added expense of a power generator. The 120-volt AC model is more popular to the contractor who will be working in areas where this type of power is readily available. Typically, you will find that these units are being used in kitchen grease exhaust cleaning, residential and industrial work where this type of power is readily available. The 240 volt pump is seldom used, because this type of power is seldom found around a power wash job site. In my opinion that high of voltage would be excessively dangerous.
These pumps (most popular bands are Shurflo and Flojet) will vary in price from $ 65.00 to $180.00 and are totally rebuildable. If you are applying large amounts of chemical on a repetitive basis, this is definitely a method to consider. You can control the chemical mixture and the flow rate much better than most other ways of chemical application.
Last but certainly not least is the application of chemicals through the use of foam generators {foamers}. There are many different styles of foamers on the market today. They vary in price ranging from $50.00 to $900.00. The advantage in applying chemicals using this method is that foam clings to vertical surfaces longer than less viscous liquids thus providing a greater dwell time for the chemical to work.
