How to Pressure Wash a House
How to Pressure Wash a House – Homeowners Practical Guide
In this guide, we will show you step by step how to wash a house. We will use a method called “soft washing”, where the detergents are relied on to clean, and the pressure washer used to apply the detergents and to quickly rinse. We will use a consumer model “Generac 3000 PSI Pressure Washer” as an example, but some details will need to be changed depending on the capability of your pressure washer.
The Generac Pressure Washer produces 3000 PSI at 2.7 GPM and has a list price of $497.51 and is available on Pressure Washers Direct for $399. The Generac 3000 PSI represents a mid range consumer pressure washer used for occasional washing, and not designed for professional use, but may be similar to what many homeowners may use to wash their home.
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, 2.7 GPM will be significantly slower but will still get the job done. 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 hose 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.
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 Generac has size “03” orifice nozzles, which at 2.7 GPM will produce approximate 3000 PSI. This is a different number than the spray angle that is color coded, a size “03” 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 2.7 GPM pressure washer.
Choosing the correct size nozzles
Looking at the Chart we see how much pressure a size “03” nozzle will produce at various GPM. Following the chart from the left, we see at 2.60 GPM a size “03” nozzle will produce 3000 PSI. This is our default tip that comes with the Generac. Going to the “800 PSI” column will go down until we see a GPM close to 2.7 GPM. A size “6” tip will produce 800 PSI at 2.68 GPM, this is the size of nozzles we want for our Generac 3000 PSI 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.
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, and a nozzle to rinse low. 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 2.7 GPM machine, we will need a 2506 “Green” nozzle for rinsing low, a 0006 “Red nozzle” for rinsing high, a 2540 “Black soap” nozzle for soaping low, and a 0040 “Black soap” nozzle for soaping high. The numbers “2506” 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 GPM 6 GPM “06”. 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
The Generac has a built in chemical injector and detergent tanks, however the tanks aren’t as easy to fill with a large amount of detergents. Instead of using the build in injector we will use a dedicated 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.
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. Avoid buying any SH with additives, fragrances, or “Outdoor” versions.
Mixing our custom soap
We will start by adding 3 gallons of 8% SH to a 5 gallon bucket. Then add 1 gallon of water. (If you can find 12% SH add 2-2.5 gallons of SH to a 5 gallon bucket and fill the rest with water) 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 “Panel Bright” and use about 1 quart per 5 gallons of SH/Water, but other products may require different amounts, again read the instructions and use less than called for. 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.
Follow your pressure washer’s instructions and attach the garden hose, pressure hose, trigger gun, and place the detergent injector in the 5 gallon bucket of detergent mix. Start the pressure washer and attach the green 25 degree 6 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.
Attach the 25 degree black soap 40 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 “Black” 40 nozzle to reach the higher areas of the siding and the fascia. Make sure all the siding is covered with the detergent. Then switch back to the “Green” 25 degree 6 GPM 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.
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.
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.
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.
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.
For very high areas of the home it is possible to use the “Red” 006 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. At 800 PSI (06 nozzle at 2.7 GPM) the “Red” nozzle is safe to use at a distance (10′ – 15′) to wash and rinse, and can be used at a closer range to wash exterior gutters.
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” “03” nozzle will produce 3000 PSI at 2.7 GPM and you will damage your 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.
Your total cost will be around $500 if you don’t already own a pressure washer. To wash a 2000 sq ft vinyl home would take about 4-6 hours if it is your first time washing. Only you know the value of your time.
Pressure Washer $400
Chemical injector $30
Hire a Pro
Another option to consider is to hire a professional to wash your home. A pro can wash a 2000 sq ft home in 1.5 hours or less and it will cost on average between $200-$400 depending on your area. You also can have the peace of mind that a pro will wash your home correctly, taking care to rinse your plants, protect the more delicate areas of your home, and properly rinse all soap residue from the siding.