How to Pressure Wash a House

This is our original "How to Pressure Wash a House" guide, first published in 2013 on our old site. We lost the backup in a later site rebuild — this version was restored word-for-word from the Wayback Machine, same photos included.

How to Pressure Wash a House – Homeowners Practical Guide

Our technician “soft washing” a vinyl gable

Intro

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.

Example Machine

Our example machine produces 3000 PSI at 2.7 GPM

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

You must not let your pressure washer idle for more than 3 minutes to prevent 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 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 an orifice sized to produce a certain PSI with the rated GPM of the pressure washer. For our 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.

Chemical Injector

A chemical injector allows you to quickly apply detergent — 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, and you need to be able to switch between two detergents while pressure washing a home. We recommend getting a stand alone downstream chemical injector that pulls detergent directly out of a 5 gallon bucket through a hose. This allows you to easily switch between detergents by simply moving the intake hose to a different bucket, and refill by simply adding more to the bucket.

Choosing a Detergent

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 a $3 jug of SH mixed with a surfactant, if applied correctly and rinsed enough the SH and detergent will be neutralized and rendered harmless and eventually it will biodegrade into salt.

Applying the Solution

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 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 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 loses concentration over time, so if you buy it well before you plan to use it, you may need to use more than expected.

Clean, rinsed siding after a finished wash

Important Note

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.

Final Cost

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.

A pro will carefully wash your home, taking care not to damage your plants, protect the more delicate areas of your home, and properly rinse.

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.

by HydroClean