Pressure Washer Chemicals
Use and Application

"If I've got sufficient pressure (PSI) and sufficient flow(GPM) to eventually loosen the grime and wash it away. Why on earth use pressure washer chemicals at all?"

Well, if you are an experienced contract cleaner then you most assuredly already know the answer to this question.

There are three prime reasons why contract cleaners make extensive use of chemicals. Those being:

1. The use of Chemicals enables a "higher quality" result.

2. Some Chemicals will extend the life of the job.

3. Using chemicals will allow a quality job to be done faster.

The first two points relate to quality and value issues for the consumer which can justify higher prices charged. The third point is simply good business sense.

For every dollar a contractor spends in fuel to heat water and chemicals to enhance productivity up to nine dollars in labor can be saved.Since labor is one of a contractors highest business expenses This 9:1 internal leverage is what makes heat and chemical use so attractive to the professional.

For the non-professional to better understand the rationale for chemical use the analogy of "washing your hands" can serve the purpose.

Cold Water and Low Pressure- Yields poor results, vigorous scrubbing required.

Cold Water and Higher Pressure- Slightly better results.

Cold Water, Higher Pressure and Soap- Good results, some scrubbing may still be required.

Hot Water, Higher Pressure and Soap- Best results, scrubbing may not be needed..

If the soap is allowed to dwell for a moment the results are even better. Hey! doesn't washing the dishes or doing the laundry work in exactly the same way?

While this may seem all too obvious, why should pressure washing be any different?

Ok,Ok already, I agree I should use chemicals. So what are the best ways to apply them?

There are three methods in general to apply chemicals and 4 common ways to do so. We'll discuss each of these along with their advantages and disadvantages. Chemicals can either be applied directly, or they can be injected into the water flow either "upstream" or "downstream" these three methods each have their advantages and disadvantages.

Pump Up Sprayers

For homeowners and occasional chemical applicators a garden type "pump up sprayer" works nicely. The advantage is that since you are not injecting chemical into a water flow you have great control over the concentration of the chemical you are applying.

The disadvantage is that this can be much slower than other methods. Sprayers designed for garden/homeowner use can and do work. But for commercial use you should consider durability, strength and quality in this instance B & G industrial sprayers are a great way to go

The next way commercial cleaners use to directly apply chemical is by means of an electric chemical pump. Generally these are either 12V or 115V systems and are mounted to a chemical tank 14 gallon and 25 gallon poly type tanks are extremely popular, just like the pump up type sprayer chemical is not being injected into the water flow so over dilution is not an issue. There are two industry leading brands for this type of pump those being ShurFlo and FloJet. Either one of these brands will give you quality performance at resonable costs.

Upstream Chemical Injection

When injecting chemicals "upstream" what you are doing is introducing chemicals to the water flow as it enters the actual pump inlet. The popularity of this type of chemical injection is due to the fact that this allows chemicals to be applied at full pressure a major advantage for productivity.

The downside ( and it's a big one) is that the inner seals ,valves and other components of the pump are directly exposed to the chemical which if too acidic or caustic can cause serious and even fatal damage to the pump. And it can do so surprisingly quickly.

When I was learning the business I was always told to only use "mild detergents" when upstreaming. This always bothered me because who is to say what exactly constitutes "mild".. So I turned to the technical department of CAT PUMPS and posed the question "what is a suitable range of pH values that can be upstreamed through a CAT PUMP?" I was thankful for their speedy reply, they advised that a pH range of 5 to 9 is suitable for upstreaming through the pump and yes, this qualifies as mild. When evaluating a pH value remember: a pH value of 7 is exactly neutral the lower the value goes the more acidic a chemical is and the higher the value the more alkalinity the chemical posseses.

Without getting too technical realize that the pH scale is logarithmic so a 1 number change in the pH scale equates to a ten fold increase in concentration in other words an acid with a pH value of 3 will be 10 times more acidic than one with a pH value of 4.

Here is a more detailed description of pH:

PH levels

The concentration of hydrogen ions in a solution is called pH and determines whether a solution is acid or alkaline. A pH value indicates the intensity of acid or alkaline conditions. In general acidity is a measure of a substance's ability to neutralize bases, and alkalinity is a measure of a substance's ability to neutralize acids.

The pH scale ranges from 1 (acid) to 14 (alkaline or basic) with 7 as neutral. The scale is logarithmic so a change of one pH unit means a tenfold change in acid or alkaline concentration. A change from 7 to 6 represents 10 times the concentration, 7 to 5, 100 times, and so on.

So, In conclusion:

If applying chemicals with pressure is vitally important to you then remember that
you must have a thorough understanding of the pH value of any chemical you are applying upstream.

Remember: pH values less thsn 5 or geater than 9 cannot be used with this method.

Special Note: Bleach commonly used as a mildecide has a pH value of about 13 and is not suitable for this method of application.

Always keep in mind: An expensive pump is a terrible thing to waste.

This method of chemical application is the most widely used in the industry today.
Mounted to the outlet of the pump a downstream injector introduces chemicals to the water flow AFTER it leaves the pump. This effectively eliminates the major risks of exposing the inner workings of a pump to harsh chemicals.

This is the preferred method for those who regularly use bleach,or chemical formulations which are highly acidic or caustic.

For system safety reasons many if not most pressure washers sold today include some type of downstream chemical injection system as a standard accessory.
Upstream injectors are never sold as a standard accessory.

Downstream injectors operate on what is known as the "venturi" principle. In it's essence, what this does is to create a siphoning action which sucks the chemical up the chemical tube and then introduces it to the water flow.

When first trying to use these injectors many people become frustrated when the injector is not drawing chemical. The problem is usually not the equipment or injector. The most common reason why chemical is not being drawn into the system is that the operator is trying to use a high pressure tip. What is happening is that high pressure tips create backflow on the injector outlet defeating its ability to create the siphoning action needed to draw chemical.

This is very simple to correct. If your system uses a (hi-low) type nozzle just set the nozzle to low. You will now see that chemical is being drawn properly.

Downstream injectors employ a check valve which will not allow water to back into the chemical tube when chemical is being applied.

These tips/nozzles create a wide low pressure fan and are used primarily for chemical injection only.

The two main complaints regarding this type of chemical application method are:

1. I can't apply my chemical at high pressure.

2. I don' feel I have good control over dilution. of my chemical.

It is my experience that a standard fixed chemical injector will dilute your chemical by a factor of about 10:1 so consider this when deciding on what concentration of chemicals to use.

Standard injectors are fixed in their rate of draw.
Adjustable injectors are sold which allow a metering knob to be turned to adjust the draw. Unfortunately very often machine vibration will loosen your desired setting.

You should know that when a manufacturer advertises a specific draw rate you will probably not achieve the same result.

Understand that the manufacturers' draw rate is derived in "laboratory conditions" usually tested by drawing water.

Your situation will never be "laboratory conditions" so just be satisfied in knowing that a higher advertised draw rate will draw more chemical than one not rated as highly.

Chemical usage can be a startling addition to your cleaning process. Chemicals can make your life easier and results far more satisfying.

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