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How to apply cleaners on the job.

Applying Cleaners: Dwell Vs. Injection Method For Pressure WashersEverybody knows by now that the key to cleaning faster with the lowest cost of labor is to use chemical cleaners to speed the job along. Most folks with time in the trade understand by now that $5 worth of cleaner can save you $25 worth of time.

The instructions on most cleaners assume that the contractor uses the dwell method of application for the product, which is not always the case. This is a great opportunity to look at the impact of different application methods on your business from a time - labor standpoint.

There are two primary application techniques contractors use when they apply cleaners to a surface.

The Injection method, including:
• Upstream Injection
• Downstream Injection
• External Injection The Dwell method, usually involving mechanical spraying (or a hand application such as brushing).

The “Injection” method describes introducing the cleaner through the water being used to clean the surface. Let’s discuss the various styles of injection applications.

Upstream injection describes a system where the cleaner is introduced into the stream of the pressure washer before the pump. That means that the internal parts of the pressure washer, such as the pump itself, are exposed to the cleaning chemical. Since so many good cleaners are either strong caustics or strong acids, the pressure washer must be designed and built to handle these cleaners.

Downstream injection occurs when the cleaning chemical is not introduced into the water until after the pump. The only equipment exposed to harmful corrosives like acid or caustic, then, are the hoses, quick-connects, trigger gun, wand, and nozzles.

External injection describes the injection of a cleaner after the stream has passed through the pressure washer, the hoses, and the wand. The cleaner is introduced to the stream at the end of the wand. The typical external injection tool is the X-Jet.

The “Dwell” method, on the other hand, describes introducing the cleaner directly to the substrate at a pre-determined strength and allowing it to sit and work on the dirt for a pre-determined amount of time. For the dwell method, no cleaning chemical comes into contact with your pressure washer.

The differences between using the Injection Method and the Dwell Method are plentiful. They include:
1. Type of cleaning equipment used
2. The surface being cleaned
3. The soil being cleaned
4. Amount of product consumed
5. Wear and tear on equipment
6. Speed of application
7. Control of cleaning action

When we talk about the type of cleaning equipment being used, we are looking first at the pressure washer. Many hot water machines come with upstream injectors because of the desirability of being able to use the cleaner at a wide range of concentrations with the full amount of water pressure available that the machine can produce. The comparably higher cost of an upstream injection system can be easily justified on a piece of equipment priced at $5000 and up. The limitations of using an upstream injector include the fact that you must go back to the power washer to regulate the flow of cleaner (turning it up or down or off). With upstream injection, you are truly applying the cleaner and the cleaning force of the water at the same time. The greatest advantage of using an upstream injector is that you can either ‘heat up’ the mix or cool it down with the turn of a knob – based on how the cleaner is working on the soil.

Many cold water machines (which have price points well below hot water machines) come equipped with downstream injection systems because these systems are less expensive and adapt well to both belt drive and direct drive applications. The best advantage of a downstream system is that you can start the cleaner flowing and stop it from flowing right at the wand. With downstream injection, you will by default be applying the cleaner at a low pressure and use a high pressure rinse to complete the cleaning job. The disadvantage of using a downstream injector is that, in order to get the perfect strength, you may have to play with the concentration of the cleaner before it goes through your injector.

When we discuss the surface being cleaned and how that affects the cleaner application, first consider soft surfaces like wood. Unable to withstand high pressure, these softer surfaces require the use of either a downstream system or the dwell method to clean with a minimum of damage. Harder surfaces such as steel or masonry respond best to cleaning with high pressure (so any cleaner application method will work).

The dirt being cleaned may require extended chemical action before it can be rinsed away. A case in point is the job of stripping a tough finish off of a deck. In that case, we have to keep the pressure light and yet we need an effective chemical cleaning action. This is a classic case for using the dwell method, where the cleaner can be allowed to sit for an extensive period and then rinsed away at low pressure after it has done its job.

Your application method greatly affects the amount of cleaning chemical you will use to get the results you want. Since a wide range of concentrations are available with upstream injector applications, and since the application and the rinse process take place at the same moment as you apply the cleaner, you will tend to use much more cleaner than with other systems. Since the output ratio of most downstream injectors is fixed, you will be limited in the strength of the cleaner but you will likely use less product. You will tend to use the least amount of cleaner for any job by using the dwell method because the product is applied at a controlled rate and allowed to work without further dilution.

When it comes to wear and tear on our equipment, remember that the cleaners we all love are extremely strong. Acids and caustics react on materials including metals like brass and aluminum, so everything from your pump, quick-connects, hoses, trigger guns, and tips can be affected by contact with them. Using upstream and downstream injectors for strong cleaners will force us to replace wear items like hoses and quick-connects quite frequently because of the damage caused. In situations like this, it is often much more economical for a contractor to switch to stainless quick-connects that will last a year instead of using brass (which will need to be replaced about every 3 months with exposure to strong cleaners). Besides quick- connects, tips and guns are among the first things to show premature wear – requiring more frequent replacement.

Nothing is faster than using an injector system to apply cleaners. With the dwell method, you must apply the cleaner and wait for it to finish its work before you begin the pressure washing process – a process that usually means about 10 minutes of wait time. With the injector method, you skip that whole step (and the associated time). You simply start washing.

The dwell method, on the other hand, gives you an extraordinary amount of control over the chemical action taking place. You control the exact concentration of product (its strength) and the exact amount of exposure time. The extra time invested for the applying pays a handsome dividend in the results possible.

If you are considering using the dwell method, you will likely be applying the product with a mechanical sprayer. This can range anywhere from the simplest “pump-up” mechanical sprayer to a complete application system like a Deckster. Many contractors have also built sprayers themselves using off-the- shelf parts like ShurFlo and FloJet motors.

Pump-up sprayers vary widely in quality, function, and price. Cheaper units have fragile plastic wands and tips, and the output can be spotty. Better units have brass wands and brass tips. The ones we sell come with a brass wand and a brass cone jet tip and a lifetime warranty. Avoid using backpack sprayers. They are a great idea in theory, but if they ever leak some pretty strong chemicals will be dripping into places you would rather not have them. (I am speaking from personal experience, so I know!)

Electric sprayers can be powered at 12 VDC or 120 VAC, depending on your situation. ShurFlo and FloJet pumps are diaphragm pumps, which require Viton kits to be added if you are dealing with strong cleaners. These motors are available from Sun Brite and work very well, with the exception of the problems that occur if they are not cleaned properly after use or when the diaphragm develops a minor leak. We often got anywhere from a year or so of service out of one of these pumps, to as little as two months (depending on the product we put through it and the way it was cared for by the employees).

Of course you knew we would mention the battery-operated Deckster. This uses a different pump from a ShurFlo-style because it is a piston pump. The pump stands up to a lot of abuse and keeps going, which is why we chose it in the first place. The Deckster will apply any product, acid or caustic. Required maintenance is minimal. The pump is economical and fast to rebuild if anything wears out. The first one we ever put into service is still in daily use today.

We have preached the gospel of the dwell method for years and years here at Sun Brite Supply of Maryland. Because we started in the business as wood guys, that method was our natural direction. It allowed us to harness the power of the cleaner at its optimal strength, and to rinse the cleaner off the surface when the dirt is ready to move easily.












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Applying Cleaners: Dwell Vs. Injection Method For Pressure Washers