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| This Pressure Pro produces 8 GPM at 3500 PSI |
Example Machine
The Pressure Pro Pressure Washer produces 3000 PSI at 8 GPM and has a list price of $3400. The Pressure Pro 3000 PSI represents a high end commercial pressure washer used for everyday washing, and is designed for professional use.
PSI vs GPM
PSI (pounds per square inch) is the force of the water, and GPM (gallons per minute) is the volume of water the machine produces per minute. GPM is a far more an indication of the power and speed of a pressure washer than PSI. A 4 GPM pressure washer is the minimum that should be considered for professional use, and 5.5 GPM and 8 GPM are more commonly used by pros. Think of the difference between a push mower and a zero-turn mower, but will cut grass fine, but the zero-turn will cut the grass in a fraction of the time of the push mower.
Preventing Pump Damage
Here is some basic info about pressure washers, once a water line is attached and pressure washer is started you must squeeze the trigger every 3 minutes (preferably less) otherwise the pump could overheat and be damaged. You cannot let a pressure washer idle for over 3 minutes at a time. This has nothing to do with relieving pressure build up (the unloader already does that) but that the friction of the water inside the pump produces heat, the the small amount of water inside the pump will continually heat up and eventually damage the pump leading to costly repairs. Squeezing the trigger draws fresh cool water inside the pump and cools the pump off. This is also compounded when it is a very hot day and the water hose is in the sun, the water is already hot going into the pump, in this case you most hold the trigger open for a longer period of time.
Professional setups bypass the water from the pump back into the water storage tank instead returning to the incoming water line. This allows the fresh cool water from the tank to cool off the pump at idle, preventing damage to the seals and internal components of the pump. This is achieved by installing a 3/8 line from the bypass port on the unloader to connection on the water tank. This is done by installing a 1/2 bulkhead on the top or side of the tank and reducing to a 3/8 barb and connecting the hose. With this setup the pressure washer can run at idle continuously without damage. The Pressure Pro 8 GPM shown above comes with a bypass line already attached and is set up to be fed from a water tank with a 1" line.
Pressure Washer Nozzles
A pressure washer usually comes with a varieties of nozzles, color coded to indicate the spray angle. (Red 0 degrees, Yellow 15 degrees, Green 25 degrees, and Black (soap) 40 degrees). Each nozzle has a orifice sized to produce a certain PSI with the rated GPM of the pressure washer. The Pressure Pro has size "09" orifice nozzles, which at 8 GPM will produce approximate 3000 PSI. This is a different number than the spray angle that is color coded, a size "09" green 25 degree tip with produce the same PSI as a yellow 15 degree tip (in this case 3000 PSI).
How to reduce pressure
We are going to "soft wash" the house, so 3000 PSI is far too much pressure to use for our purpose. We want to use between 800 - 1200 PSI to wash the home, so how do we accomplish this? One way is to reduce the throttle of the engine, this will reduce the RPM that the pump is running at and also reduce the PSI. However this will also reduce the GPM of the pressure washer which will make the washer much less effective. The best way to lower the PSI and maintain the rated GPM is to use tips that are a larger sized than the ones designed for the pressure washer. We will use the chart below to determine the right sized tip to achieve soft washing with a 3000 PSI 8 GPM pressure washer.
Choosing the correct size nozzles
Looking at the Chart we see how much pressure a size "09" nozzle will produce at various GPM. Following the chart from the left, we see at 8 GPM a size "09" nozzle will produce 3000 PSI. This is our default tip that comes with the Pressure Pro. Going to the "700 PSI" column will go down until we see a GPM close to 8 GPM. (In this case 8.37 GPM) A size "20" tip will produce 700 PSI at 8 GPM, this is the size of nozzles we want for our Pressure Pro to "soft wash" the home. You will have to use the chart to find the appropriate nozzles for your size pressure washer based on your rated GPM. You will use the higher pressure 700 PSI nozzles to wash brick up or wood close, to spray metal gutters with more pressure to remove mold, or to more easily remove cobwebs and debris from high distances. With 8 GPM it is possible to rinse the home with very low pressure nozzles, less than 100 PSI. From the chart below we can see that a size 60 nozzle produces 100 PSI at 9.49 GPM so with a 8 GPM machine we can rinse the home using low pressure 60 orifice nozzles that we also use for soap.
The four nozzles you need to "soft wash"
Now that we know what size tip to use we need four pressure tips, a nozzle to apply soap high, one to apply soap low, a nozzle to rinse high with more pressure, and a nozzle to rinse low with more pressure. Depending on your location it may be hard to find a varieties of pressure washing nozzles in local stores. In that case you will have to order the nozzles on the internet. Northern Tool usually has a good selection of nozzles and you could check there for the appropriate nozzles for your machine. Based on our example 3000 PSI 8 GPM machine, we will need a 2520 "Green" nozzle for rinsing low, a 0020 "Red nozzle" for rinsing high, a 2560 "Black soap" nozzle for soaping low, and a 0060 "Black soap" nozzle for soaping high. The numbers "2520" are usually imprinted on the end of the nozzle. The first to numbers is the spray angle 25 degrees "25", the next two numbers are the rated orifice size "20". Unfortunately you may find it hard to find a "0040" 0 degree black soap nozzle in a store. In that case I recommend going to www.pressuretek.com to find a 0 degree soap nozzle. The 0 degree soap nozzle is essential for applying soap to the higher areas of a home. We use a JROD 4 way nozzle holder that holds 4 1/4 meg nozzles at once which gives easy access and makes it harder to lose the nozzles.
Downstream chemical injector
We will use a dedicated chemical injector. You may be able to find one at a local store, or you can order a chemical injector from www.pressuretek.com or another online pressure washing supply store. The chemical injector has tube which is placed in a bucket of mixed detergent, and draws the chemical into the pressure washer hoses when a soap nozzle is attached to the trigger gun. Then by switching to a higher pressure tip, the soap can be emptied out of the lines so it is possible to rinse with water. When Soft Washing with the 8 GPM Pressure Pro we will not be using the chemical injectors feature of turning off with higher pressure tips. Instead we will move the detergent line to water to rinse or install a 1/4 shutoff valve to turn off the detergent while we rinse with less than 100 PSI nozzles.
Detergent solution
What is the best pressure washing detergent for washing homes with mold and mildew? The best detergent for pressure washing houses is a custom mixture of a soap surfactant to help the mixture "stick" on vertical surfaces and Sodium Hypochlorite to dissolve mold and mildew. Sodium Hypochlorite (SH) is very common chemical in today's world. It is used to clean clothes, purify water, clean pools, and found in numerous household cleaners. Sodium Hypochlorite is also best chemical to kill mold & mildew found on the exterior of homes. Sodium Hypochlorite is produced by electrifying salt water and is very inexpensive. Since it is so inexpensive and effective companies can't brand and market it effectively for pressure washing use. They create proprietary detergents with brand names and do everything possible to disparage Sodium Hypochlorite by saying it is "dangerous, ineffective, and bad for the environment." None of these things are true but are just marketing ploys so you will use their $20/gallon soap instead of $1.50/gallon SH. Sodium Hypochlorite is commonly marketed as bleach, and is best found in a more concentrated form at chemical or pool supply companies. However you can still use store bought bleach, it's just weaker and much more expensive. You can find SH at Walmart for about $3.00/gallon at about 8% strength. This means we will have to use it without watering it down otherwise it will be ineffective. For pros it is recommended to find a local supplier of 12% SH which gives more flexibility in mix ratios and can be bought more cheaply at greater quantities. In this area a 55 gallon of 12% SH costs just over $100.
Mixing our custom soap
We will start by adding 2.5 gallons of 12% SH to a 5 gallon bucket. Then add 2.5 gallons of water. This is our "House Wash" mix. We also will need some form of detergent (soap) to mix with the solution. The brand of detergent isn't very important, any commonly found products that are designed for pressure washing will work. Some products you may consider are Simple Cherry or Cleansol BC. Read the directions on the detergent container on how much to add per gallon, and use about half the recommended amount. The directions are intended for using the soap without mixing it with SH and in our experience you don't need as much soap as the directions call for. We use a soap called "Elemonator" and use about 5 ounces per 5 gallons of SH/Water, but other products may require different amounts, again read the instructions and use less than called for. Now we will fill a 5 gallon bucket with straight 12% SH. Add the same soap quantity as in the first step. This is our "Strong Wash" mix. We use this for very difficult mold and for spot cleaning. Once we drop our chemical line in our custom soap, the chemical injector will mix the soap with water further diluting it from 12:1-18:1 making it the perfect strength to use on siding. For contractors larger mix tanks are more efficient. We use 10 gallon tanks and 35 gallon tanks with the same 1:1 mix ratios for House Wash and straight for Strong Wash.
Soaping
Follow your pressure washer's instructions and hose, trigger gun. Start the pressure washer and attach the green 25 degree 60 GPM nozzle. Make sure that every time you change nozzles that your quick connect is fully engaged. If it is not fully engaged and "locked" the nozzle will shoot off the end of the lance when you squeeze the trigger and you could possibly lose the nozzle or break a window.
Remember to always point the wand in a safe direction before first pulling the trigger, the initial "burst" of pressure is greater with the first pull and then is reduced to a steady flow. If you are aiming at something, this burst could possible damage it or cause you to lose balance.
Pre-wet any plants that are below the area to be washed, aim above the plants at a distance and allow the mist of the spray to wet the plants. Don't aim the pressure washer directly at the plants or get too close otherwise you will damage the plants.
Place the detergent injector in the 5 gallon bucket of detergent "House wash" mix. Attach the 25 degree soap 60 tip to the pressure washer, move closer to a the siding away from any plants and spray the wall until the chemical injector draws detergent, you should be able to tell by the soap bubbles.
Start from the bottom and apply the detergent to the siding as far up as you can reach. Then switch to 0 degree 60 nozzle to reach the higher areas of the siding and the fascia. Make sure all the siding is covered with the detergent. You do not have to "saturate" the surface, just "wet" the surface with the detergent. The secret of efficient washing is multiple quick applications, not long saturating applications that just waste detergent on the ground. Then switch back to the "Green" 25 degree 60 orifice nozzle and spray the siding away from plants to empty the detergent from the lines.
Then immediately rinse any windows from a distance to prevent the solution from drying on the windows. Never spray windows up close with pressure, this can break the vapor barriers of the windows causing them to fog. Always rinse the windows at a distance with low pressure.
Once approximately 5 minutes have passed, apply a second application of "House Wash" mix to the siding. You can move faster now that you are re coating the surface. Pros will coat a larger area (two sides of a small to medium house), then walk back to the start for the 2nd application. By the time they have finished the 1st application, the starting area is ready for the 2nd application and no time has been wasted.
You should see the mold begin to turn brown and run down the siding, if there any areas still containing mold after a few minutes reapply the detergent solution to those areas. If there are any very stubborn mold spots you can use pressure up close to remove them, or use a brush or rag if you can reach the area. Also note our solution will only effectively remove mold, if there are clay stains, grease stains, or heavy dirt stains on the siding you may have to switch to a stronger soap solution or brush the area to remove the stains.
After two applications of "House Wash" check the gutters and siding for any stubborn mold spots that remain. If you still see mold, switch the detergent injector to the "Strong Wash" bucket and spot clean the mold areas only. You can use the 0020 tip to clean the outsides of metal gutters to remove stubborn mold, be careful not to hit the shingles or siding with that tip. You can also use a brush to speed up removal of stubborn areas on gutters and siding while not waiting for the SH to work.
Heavy clay and rust stains need an acid based detergent for removal, OneRestore by EaCo Chem is the best that we have found, however it is expensive at $20/gallon or $100/5 gallons and you must use it straight or 1:1 applied with a pump sprayer. Note you cannot mix acid based detergents with alkaline detergents such as soaps or SH.
If the detergent does seem to be removing the mold by itself, you can increase it's strength by adding more SH to the mix. SH has a limited shelf life and can lose strength over time or if exposed to sunlight. Experiment until it begins cutting through heavy layers of mold by itself, with soft washing the detergents alone should do the cleaning, you shouldn't have to use up close pressure to remove the mold and mildew.
Washing
Once all the mold is dissolved then you need to "soft wash" the siding. Starting at the top of the quickly wash the siding making sure to cover all the surface area. Work your way from the top down washing away debris as you go. Try to wash away all wet debris that may be stuck to the siding during this step. With 8 GPM we can use the soap nozzles to rinse, it makes it easier and more efficient than using higher pressure. On smaller pressure washers you may have to use the higher pressure nozzles (700-1200 PSI) to effectively reach areas.
Rinsing
Remove the detergent injector from the soap and turn off the shut off valve on the line if installed, or place the detergent injector line in clean water. With an 8 GPM washer you may want to remove the chem injector entirely during the rinse process or build a "Detergent injector by-pass system" because the chemical injector reducing the flow of a 8 GPM pump, limiting your rinsing ability.
After you have washed the siding, you now need to thoroughly rinse the siding from top down. Hold the stream of water over an area and let the water "cascade" like a waterfall as you slowly move down the siding. Do this in sections and completely rinse the siding. A good rule of thumb is when you think you have rinsed enough, rinse again the same amount as the first rinse. Rinsing is critically important. You must rinse off all the soap from the siding to prevent the soap from drying on the surface and possible causing oxidation (hazing) of the siding. Make sure to apply an extra rinse to windows. Then rinse the any plants as you did in the pre-wetting process. Take extra time to rinse the plants, and rinse anything else the soap detergent could have been blown onto (cars, furniture, etc). With enough rinsing the SH and detergent will be neutralized and rendered harmless and eventually it will biodegrade into salt.
Important Note
For very high areas of the home it is possible to use the "Red" 00 nozzle to wash the fascia and siding more easily. This nozzle should not be used close range and can damage objects including exterior lighting, siding, etc.
You cannot use a "Red" nozzle that came with your pressure washer or is not rated to operate at low pressure with your pressure washer. Using the "Red" "09" nozzle will produce 3000 PSI at 8 GPM and you will damage a home by using this nozzle at that PSI. You must select a size nozzle that produces low pressure using a nozzle chart. A High pressure "Red" 0 degree tip will draw lines in your siding, concrete, wood or whatever else you use it on. If you don't have a thorough understanding of this do not use the "Red nozzle" at all. You have been warned.
by Jason Murphy
President
HydroClean Pressure Washing Corporation
www.pressurewashinghickorync.com
