Power Wash Basics

Electric VS Gas Pressure Washer

Man spraying power washer with text "Electric vs Gas Powered Washer

       Purchasing a new pressure washer is no easy task. There are so many options to consider and the cost can be a challenge. You want to make sure you are making the right decision and choosing the right pressure washer for your business needs. The good news is that with a little research, you will be able to find the pressure washer that fits the unique wants and needs of your businesses.

         The two main options when purchasing a pressure washer are electric or gas powered. Neither is necessarily better than the other, and which one is right for you depends on a variety of factors. On the one hand, electric pressure washers can be used indoors, but gas pressure washers can pack more punch! We’ll explore the differences and options available for both electric and gas powered washers and help you make an educated decision.

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Pressure Wash Maintenance

You should always use the engine manufacturer's suggestions as a minimum standard for maintaining your pressure washer. Consult your owner's manual for specific information such as capacity, type, and viscosity. You should Always your oil prior to starting your engine. Check the oil daily, or after every 8 hours or more if recommended by manufacture. Most engine manufactures have a website where you can find this information if you misplaced your owners manual. If you require more information about an engine that is not listed contact the manufacturer of your pressure washer or the distributor from which you purchased the machine.

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How to Find the Right Chemical for a Pressure Washing Job

Never assume that the job you are cleaning today can be cleaned with the same chemical and technique you used on another job yesterday. No two jobs are exactly the same even if they look similar. Experience will help you become familiar with each type of surface contamination and know how to find the right chemical. No single chemical will work on every job. Professional cleaners should work on developing an arsenal of detergents for all of the various situations they encounter.

Soaps are formulated to break the surface tension that bonds the stain to the surface that is being cleaned thus allowing the flow of water to float the contaminates away. Some examples of this type of detergent would be Pink Thunder Truck Wash Soap, and R-111 Classic Brown. They can be applied with a pressure washer at high or low pressure or brushed on and rinsed off for truck washing.

Corrosives are designed to dissolve the grime. Examples of this type of chemical would be V-502 Kitchen Exhaust Grease Fighter and Clearly Clean X-Treme Concrete Cleaner. These types of chemicals should not be run through a pressure washer pump because they can do serious damage to the internal components. Use a pump up sprayer, an airless foamer, or an X-jet to apply these chemicals. Then rinse them away with a hot water pressure washer.

Sodium Hypochlorite is used where the surface contaminant is alive, such as algae or mold. The objective is to kill the contaminant and retard its regrowth. It can also be used to bleach surfaces and brighten concrete. Sodium Hypochlorite does not need pressure or agitation to work. This type of cleaning is commonly called soft washing and it is used for soft surfaces like asphalt shingle roofs, wood decks, stucco, soft stone, and color safe fabrics. There are many devices that can be used for soft washing. We recommend the Mustang.

It can be difficult sometimes to find the right chemical, but mixing your own chemical blends is not recommended. If you don't have a basic familiarity of chemistry, mixing chemicals can yield unexpected and potentially dangerous results. Exothermic reactions occur when strong acids are mixed with water. Toxic gasses can be produced when chemicals like bleach and ammonia are mixed. We receive calls all of the time from people who have damaged a customer's property with a homemade chemical blend. All of our chemicals have been tested to make sure that they will work as advertised, and all vital information is provided on a Safety Data Sheet. A Safety Data Sheet contains information about potential health risks, storage instructions, spill procedures, hazardous components, physical data, fire and explosion data, reactivity and first aid information. All of our chemicals are registered with poison control and they have instructions for treatment right on the label in case of a medical emergency.

If you are looking for a faster way to clean any project, call our experts at 1-800-433-2113. We have a range of concentrated chemicals and detergents that can be mixed to be strong enough for even the toughest stains. We also have sample sizes available so that you can test several options and find what is best for your specific needs.

Downstream Chemical Injector vs X-Jet and the X-Jet M5

In the early days of the power washing industry, contractors relied heavily on high pressure and hot water for most cleaning jobs. In those days, chemicals were milder than modern chemicals. They were injected before the pump and carried through the entire pressure washer system to eventually emerge super-heated from a high pressure nozzle. In time, we learned that high pressure can be more damaging to surfaces than proper chemicals. Modern contractors use chemical to break surface tension, pressure to agitate stains, and water to float them away.

Many chemicals that are used in the power washing industry today will damage your pump due to their harshness so they must be applied after the pump.  This type of chemical injection is referred to as downstream chemical injection.

Downstream chemical injectors are designed to be mounted as close to the pump as possible. They work on a venturi draw principle. The faster the water travels by the venturi the greater the amount of vacuum it will create. The vacuum suction is needed to draw chemicals from their holding tank. Any restrictions that are placed in the discharge line such as high pressure spray tips, extra pressure hose etc. will slow down the water, and lower the vacuum at the venturi until it stops drawing chemical. The spray tip must have a large orifice to lower the pressure and cut down on restriction. But, lowering the pressure at the nozzle will limit the amount of pressure hose that can be used with this style of injector. Even with all of these issues, the downstream injector is still the chemical application method of choice for most power washing contractors. However it is for these reasons that the X-Jet has become so popular in building cleaning.

Chemicals that are commonly used in the mobile power washing industry often need to be applied to areas that are beyond the reach of the normal application tools and methods without the use of a ladder. Climbing up and down a ladder is not only tiring and time consuming but it also presents safety issues as well. Ladders won't work in all areas. The ideal situation is to be able to stand on the ground to apply the chemicals.

The X-JET Original was designed with this thought in mind. It serves as a chemical injector and a nozzle as well. It is mounted at the end of the wand instead of at the pump. The X-Jet comes with 15 feet of chemical pick-up hose and a set of chemical proportioners that will allow you to draw chemicals at a ratio of 2 to 1 all the way down to 480 to 1. Using this device you can project a chemical and water mixture up to 40 feet. This means that when you are cleaning a building you can easily reach up to the top of a 3 story building while standing on the ground. Since you have a 15 foot chemical pick-up hose you can cover a lot of area in a short period of time without needing to move your chemical supply so often. The gallons per minute and pressure of the pressure washer that you will be using must be determined prior to choosing the size of X-Jet that you will need. The X-Jet is rated for pressures up to 5000 psi.

The X-JET M-Jet M5 will do a similar thing however it is designed with an adjustable spraynozzle that allows the user to select a wide fan pattern for covering large areas more efficiently. The wide spray patterns will not project as far as the straight stream will but for the lower areas it will allow you to move much faster because you can cover wider areas with a single pass of the wand. The spray pattern being adjustable allows you to select the pattern that you require for the particular job.

If you should decide to purchase a downstream injector, X-Jet or even a spray tip you will need to know the volume and pressure of the machine you intend to use.

How to Use Downstream Injectors

Downstream injectors are a very useful tool to have for applying soaps, detergents and acidic solutions. They allow the operator to apply detergent with a power washer which can be a very fast and effective way to get a cleaning solution to the surface saving the operator considerable time. And we all know that time is an extremely valuable asset.

There are many cleaning solutions that require the use of a downstream injector because the solution is too corrosive for the pressure pump and or other components on the power washer. Since the downstream injector can be inserted on the pressure side of the pump after those components it allows the chemicals to be used without damage.

Another feature of using a downstream injector is that unlike upstream injection, the pump does not have to work under a vacuum to draw detergent. This puts less stress on the packing of the pump meaning it will last longer before it will need to be replaced.

The best place to install the downstream injector is to attach quick couplers to both ends and insert it where the pressure hose connects to the power washer. If you are using a hot water power washer then insert the injector where the water exits the burner or the hose reel. The rule of thumb is to insert it at the entry point of the pressure hose. This prevents all the components of the pressure washer from the harsh effects of aggressive chemicals.

A down stream injector works by Venturi effect. Simply put this means that the water from the pressure washer is pushed into a constricted section in the injector. As a result the increased velocity of fluid creates a vacuum, drawing in the solution. There is still pressure prior to the injector but there is a significant drop in pressure after it. Using a low pressure nozzle at the wand will normally allow the down stream injector to work correctly.

Three things will cause the injector to stop working. One is the use of a high pressure nozzle. The benefit of this is that it allows the operator to switch nozzles from low pressure applying detergent to high pressure for rinse. Many find this to be a huge benefit of using a down stream injector because they don't have to constantly keep returning to the power washer to turn off the soap. Second is using too much pressure hose. The more pressure hose the more resistance there is to push the water through the hose. This creates back pressure and reduces the velocity of the fluid through the constricted area in the injector. So typically the injector will work up to about one hundred and fifty feet of pressure hose before it stops drawing chemical. And finally, gravity will impact the injector. As the low pressure nozzle gets higher than the down stream injector the back pressure increases until it reaches the point that it will no longer draw chemical. This usually begins to happen at distances of ten feet and higher, and can be less based on the length of pressure hose.

This article was published in our weekly addition of Spray Tips™ from PowerWash.com if you would like to receive future newsletters please click on this link: Spray Tips

Pressure Washing In Cold Weather Hints and Tips

    • DO NOT LET YOUR WASHER FREEZE! If possible, store your pressure washer in a warm place. Automatic bathroom or "Milk House" electric heaters work well in small areas like small garages and inside of enclosed vehicles (vans, bobtails, trailers).For Natural Gas and LP Gas water heaters the pilot lights provide heat at the base of your heater coils. Block off the stack to capture additional pilot light heat.Heat lamps or 500 watt halogen light next to the pump under a tarp or cardboard box helps protect the pump. If you cover the entire wash rig with a tarp you can protect the entire rig if it’s not too cold for too long.Automatic kerosene (torpedo heaters) & Natural Gas heaters will protect larger areas. Connect these to automatic thermostats. Thermostats on short plug-in extension cords are about $35.00 at your local hardware store.Infrared LP gas heaters also work well. Heat from these heaters can be quite intense so watch for fire hazards.Water Tanks can be kept from freezing over night by installing recirculating water pumps to keep the water moving. Install a water filter to clean your water as it is recirculating.If you heat the inside of an enclosed vehicle (Bobtail or Van) with snow or ice on top you may melt the snow or ice. When the water runs down the sides of the vehicle this may freeze again locking the doors and windows in place making it difficult to gain entry.An enclosed vehicle (van, step van, bobtail, enclosed trailer, etc.) offers protection against theft in addition to weather protection. Insulate the inside of your vehicle for additional protection against the cold weather. If you store your vehicle inside of a heated garage short travels of an hour or less can usually be made without the pressure washer freezing.A lot of garages and garage doors are un-insulated. Insulating the garage and garage doors offers additional protection against the cold weather. Light weight Styrofoam panels are easily attached to garage doors.Caution: Do not put combustibles next to your heat source, or items that could melt.

    • If your washer is going to freeze, the best way to protect your washer is with automotive anti-freeze, RV anti-freeze, or windshield washer fluid (Note: Be sure and check the freezing point of the fluid you are using. Some windshield washer fluids do not protect below freezing). Fill up your empty float tank with anti-freeze then start up your washer and push out the water with anti-freeze, (Note, most hot high pressure washers hold about 5 gallons). Remove your spray tip from your wand and insert it into the float tank. Re-circulate the anti-freeze for 2 minutes while turning the Trigger Gun on and off to force antifreeze into the by-pass line of the unloader. This will protect your pump, coils, hoses and plumbing. This should protect everything except the chemical line hose which you will need to do separately while recirculating the antifreeze.Use a 5-gallon jug to capture the anti-freeze for reuse. If you start out with 5 gallons of pure antifreeze it should last you all winter if you recapture it each time. If you have any questions on this call Mark Demko, Larry, or Robert for technical support at: 800-433-2113.If your unit does not have a float tank, use a 5-gallon bucket and insert the water intake hose into it.For pressure washers without float tanks that are hooked to water tanks you can install a 3/4" or 1" 3-way ball valve (T-valve) with a short piece of hose in the inlet water line to introduce the antifreeze with. This way it is not necessary to disconnect the water line from the water tank.


  • The next best way to protect your unit from freezing is to blow out the water with air pressure. Be careful with this method. Water will collect in low places and still break your washer. This is especially true if you move your washer after blowing out the water on vehicle mounted pressure washers. The vibration will collect water droplets in low places, especially in the heater coils.The packing and the valves in the high pressure pump may not completely dry when blowing out the water with air. If you start up the pump before it thaws out the valves may stick closed and the packing may stick to the ceramic plungers and tear it up.An emergency supply of air is the "canned air" sold at auto supply stores for emergency tire inflation.

  • Your washer will freeze going down the highway with a reported air temperature of 35 degrees Fahrenheit. That is because of the cooler temperatures in low places. Remember that air temperature varies normally 2 to 6 degrees in a given region going up and down high and low places.

  • In calm air hot water washing can be done to 15 to 25 degrees Fahrenheit. It depends on how your customer can tolerate ice on the ground or pavement (See the next item). In blowing wind hot water washing can be done to about 34 degrees Fahrenheit. If possible wash in direct sunlight to take advantage of thermal heating.

  • If your wash water runs across sidewalks or driveways and freezes, salt or sand these areas down for safety. Always carry a bucket of rock salt or sand for your customer's safety. Note: Rock Salt will give the people a rough surface to walk on for better traction.Calcium Chloride and Magnesium Chloride are also use for melting ice. However, these products leave an oily residue and present a "slip" hazard. Magnesium Chloride is a naturally occurring salt that is mixed with anticorrosive agents and sprayed on roads prior to winter storm to prevent ice from forming and bonding to road surfaces. There have been some health and corrosion issues with Magnesium Chloride which is used primarily in the states of Alaska, Idaho, Utah, and Washington.Rock Salt presents a maintenance and corrosion issue. And the dyes in some ice melting chemicals can stain shoes, side walks, door frames, carpets, etc.

  • Aluminum brightening and acid cleaning do not work well below 60 degrees Fahrenheit. Remember the sun, direct sun light will raise surface temperature several degrees.

  • You can pull open trailer wash rigs with water tanks down the highway in freezing temperatures by putting your wash wand into your 500 gallon water tank and firing up the water heater and recirculating the water as go down the road. If you are only going a short distance or if the temperature is not very cold (like 15 to 20°F) it may not be necessary to turn on the water heater. In this case this procedure will also work for cold water pressure washers connected to water tanks.

  • Keep your water supply hoses flowing with water, water out of the ground will be about 50 degrees Fahrenheit in most areas. If your water supply or high pressure hoses run across the cold ground they will freeze in a few minutes in sub-zero temperatures.

  • The average ground water summer to winter water temperature variation is about 30°F. Most oil fired high pressure water heaters raise the inlet water temperature 120 to 140°F with the burner running continuously. With the reduction of inlet water temperature in the winter you need to increase your fuel nozzle one or two sizes. Then in the spring you need to change the fuel nozzle again and reduce the fuel nozzle by one or two sizes.

  • Chemicals work slower in cold weather. Plan on using more chemicals and extra dwell time for the chemicals to work.

  • Do not let your chemicals freeze. Store in a dry, warm place. Liquid chemicals will usually separate upon freezing.

  • Protect yourself in cold weather with: 1) rain suits, 2) over shoes, 3) hard hats with rain troughs to keep water from going down the back of your neck and with face shields to protect your eyes and face, 4) thermal underwear, and 5) gauntlet gloves with jersey inserts. Turn the gauntlet back so that water will not run down you arm. 6) Keep extra dry gloves available.Exercise caution as ice may form on your gloves, hard hat, shoes, etc.Winter clothing generally arrives at stores in September. If you wait until cold weather occurs your store may be out of the items you need. Plan ahead and buy while the selection is the greatest.

  • On days you cannot wash do sales calls and equipment maintenance. Call Powerwash.com at 800-433-2113 and order spare parts. Plan ahead and save time.

  • Below freezing work: vent-a-hoods; in-plant cleaning; produce warehouses, limo garages, inside factories, automotive garages, car dealer repair shops, de-icing of: aircraft, oil field drilling rigs, refineries, manufacturing plants with outside water piping, etc. Look for anything that will be inside cleaning with a pressure washer.

  • You can drain your water hose by disconnecting it at each end, laying it out in a straight line, and then walking down the hose passing the hose over your shoulder.

  • Be careful where you point your spray: door locks, brake drums, door jams, and steps will freeze after you spray water on them. If you use 180 degree to 200 degree Fahrenheit, hot water evaporation will help minimize the icing problem. Sometimes you can minimize the freezing by opening and closing doors and operating the locks. Also you can spray with WD-40 with the long red needle adapter into door locks and mechanisms. Put some WD-40 on a rag and wipe on the rubber weather seals of the doors.

  • Sheathing Wax added to the rinse water like W-200 Spray Wax will help the water slide off faster, thus speeding the drying process, and reduce icing. Depending on the temperature a leaf blower may also help in blowing off the water to reduce icing. This also can increase the freezing rate if not used properly.

  • When washing reefer trailer make sure the units are running, this will help minimize icing.

  • Avoid washing in the shade. Direct sun light heats up skin temperature rapidly. Try to have the fleet owner park vehicles in the sun. The hottest part of the day for Deck Cleaning is 11:00 am until 3:00 pm.

  • If you walk on a lot of ice, use boot chains or shoes with spikes. Remember ice is really slick. Caution: The force from the surge of pressure at the trigger gun from a pressure actuated unloader can slide you backwards on ice or knock you down! While the force at the trigger gun from flow actuated unloaders may slide you backwards.

  • Mount your pressure washing equipment in an enclosed trailer, Bobtail Truck, or Step Van and insulate the inside.

  • Start your washing activities later in the day after the sun has had time to warm items up, like after 10:00 a.m.

  • Drop a small electric water pump (like those used for waterfall displays) with a 3' hose attached into the water tank. Water in motion will delay the freezing of the water tank. Also small submersible water heaters work good in water tanks for keeping the water above freezing.

  • When traveling short distances you can disconnect your pressure washer from the water tank and only antifreeze the pressure washer, hoses, etc. Put a plug into the water tank. When you arrive at the job site remove the plug and use a screwdriver and knock out the ice.

  • Where practicable cover exposed piping with heat tape. Freeze-protect outside faucets with heat tape or freeze proof valves.

  • You can remove ice from house gutters by heating up the gutter from bottom and sides then removing the ice by hand in 3 to 5 foot sections. Average size home can be done in about an hour.

  • Use indoor fittings with garden hose hook up for the sinks when outside faucets are frozen.

  • If at all possible never travel with your water tank half full. The surging of the water can push you out into an intersection or make you lose control under slippery conditions. Always check the brakes at the beginning of each day!

  • Common add on businesses for supplementing income during the winter months: 1) window washing, 2) New construction cleanup of houses for final walk-throughs, 3) snow removal, 4) chimney cleaning, 5) carpet cleaning 6) yard work and maintenance cleanup, & 7) indoor painting.

  • The best way to keep air lines from freezing is to have one continuous line with a moisture filter at the Compressor. Be sure and drain the Compressor Air Tank regularly to remove the condensation.

  • Window washing can be done in the winter time in below freezing weather. Be aware of the following: Double pane windows freeze faster than single pane windows because single pane windows get heat from the inside; use warm water but not hot water because you may crack the window from thermal stress; add 1/2 to 1 gallon of windshield washer fluid or methanol to a 5 gallon bucket of wash water.

  • Window washers commonly add "Methanol" to their wash water to keep it from freezing. This solves the water freezing problem but not the hand freezing problem. Some Power Washers also use this technique and add Methanol to their wash water. They purchase the Methanol from their Oil or Diesel Fuel Supplier or a Solvent Specialty Company by the 55 gallon drum. How much to add. Depends of the ambient conditions. Start out at about 5% and adjust from there.

  • Winter Storage of Pressure Washers:A. Antifreeze your pressure washer per instructions above. Use automotive antifreeze for storage of your pressure washer. I have personally seen units stored over 5 years with automotive antifreeze with no problems except to clean and free up the pump inlet valves.B. Get a Fuel Stabilizer from an auto parts store and add to the fuel tank to keep your fuel from turning into varnish and having the gaskets in the carburetor go bad.C. Remove the spark plug wires; spray WD-40 into the carburetor while turning over the engine to coat everything with oil.D. Remove the spark plugs and spray with WD-40 into the cylinders or put in some "Marvel Mystery" brand oil. Turn over the engine a few times to coat the cylinder walls.E. Change the engine oil, oil filter and fuel filter. If you do not change the engine oil the sludge will collect on the bottom of the oil pan and solidify. If there is any water in the fuel filter it may freeze and break.F. Top off the Fuel Tank to keep moisture from condensing inside the fuel tank. This will cause rusting of steel fuel tanks and water in the fuel.G. In the spring put in fresh fuel, replace the spark plugs, and start it up. If it is hard to start spray WD-40 into the carburetor intake the same way you would starting fluid. This gives an easier ignition than starting fluid.H. Disconnect the battery to avoid a trickle discharge.I. In the spring de-lime the coils with Scaleaway De-liming Acid and add "Red Devil Soot Remover" to your Diesel or Kerosene for your burner. Put a trickle charge on your battery for a couple of hours assure a full charge before starting with WD-40 to establish fuel flow.

  • Kitchen Exhaust Cleaning. When finished have one person turn on the fan on while a 2nd person sprays deicer on the fan. Then leave the fan on. This assures that the fan works and is not out of balance when the morning kitchen crew arrives.

  • Use fall protection equipment when on roofs. You may want to hose down the roof and melt the ice and snow.

  • Sealing Decks: You need 12 to 24 hours of drying time above 50°F before sealing a deck. Use a moisture meter to be sure the deck is dry enough. Follow the manufacturer recommendations of your Deck Sealer you are using. Some Contractors have cut off dates like October 31 of each year to stop sealing wood (Decks, fences, roofs, etc). Decks will be warmest from 11:00 am until 3:00 pm.

  • At what temperature do you quit washing? This is a safety issue. 1) Is it safe to drive on the roads? 2) Can you arrive at the job site safely and without the equipment freezing up? 3) Will you have a safe surface to walk on? Will you be on a roof? Sidewalk? Ice or Snow? Scaffolding? 4) Can your employees drive to work OK? 5) Will the freezing of the waste wash water be a problem? 6) Can the washing be done safely? 7) What will other traffic be like and how skilled are other drivers? What are the chances of a traffic accident?

  • When removing large chunks of ice from vehicles use your zero degree nozzle to cut the ice into small sections. Then direct your spray to break off these smaller sections. This is faster than simply melting the ice. Caution: Beware of flying chunks of ice!

  • Preventing your Bay Doors from Freezing:A. If you have steel rollers change them to magnum type rollers.B. Install proper weather stripping around the door.C. Make sure the door is well lubricated and serviced.D. Insulate the door with Styrofoam panels is not insulated.E. Install a heater at the threshold of the door.H. Keep only one door open at a time to avoid a creating a wind tunnel.

  • Keep pressure hoses and airlines in the cab of the truck to prevent freezing on the way to the job if needed.

  • If you suspect that your pressure washer is frozen proceed with caution:A. Try to rotate your pump by hand to see if it will turn freely. Practice this during warm weather so that you will know what the resistance feels like and you can recognize a frozen pump. Disconnect the spark plugs when doing this to avoid the engine accidently starting.B. Do not turn the burner on until water flow established. Frozen controls may allow the burner to fire without water flow. This could result in a steam explosion.C. It will take about 12 hours in a heated area to thaw out a frozen pressure washer.D. Failure probability due to freezing is: 33% chance of no damage, 33% chance of delayed failure which will occur in 90 days, 33% of immediate failure.E. Caution: We have had Contract Cleaners add gasoline to their kerosene and diesel fuel in order to make the burner hotter. This has resulted in a melt down and failure of the burner assembly. If you need more heat increase the size of your burner nozzle one or two sizes.

  • Hair Dryers and Heat Guns are safer than torches when thawing things out.

  • Tips for pouring concrete:A. Order concrete made with hot water and increase the cement content by about half a bag. Exact amount will depend on the conditions and thickness of the concrete.B. Order air-trained concrete. This provides additional protection against freezing.C. Order low-slump concrete to ease finishing.D. Do not pour concrete on a frozen surface. This includes frost, ice, and rebar that is covered by frost or ice. When poured on frozen ground the concrete will settle as the ground thaws.F. Surfaces and concrete can by insulated with straw, plywood, insulating blankets, or fiberglass insulation between 4 or 6 mil polyethylene sheeting. Polyethylene sheeting alone may be OK if the temperature does not get much below freezing. New concrete should be protected from freezing to avoid cracking or flaking off.H. Place extra insulation around the edges. Faster cooling here can cause cracking. Make sure the concrete cools slowly over two or three days.I. Calcium Chloride flakes or pellets may be placed under the insulation to produce heat. Caution: Calcium Chloride tends to discolor and produce efflorescence.J. Under severe conditions a heat enclosure may be required for several days before the ground is thawed out. Caution: Excessive direct heat can blister the top layer of concrete and cause personal injury. Make sure the enclosure is properly vented.K. Concrete needs to be at least 55 degrees at pouring and 50 degrees for two days.

By: Robert M Hinderliter, Powerwash.com, 2513 Warfield St., Fort Worth, Texas 76106-7554. email: robert.hinderliter@powerwash.com ; URL: http://www.powerwash.com ; Phone: 800-433-2113; Fax: 817-625-2059.
Copyright 2011. Powerwash.com. All rights reserved.


What is Cleaning Units - PSI - GPM - Nozzle Size and More

Understanding Cleaning Units

Cleaning Units: What it Means
Summary: The Power Washing industry expresses cleaning power as either “Cleaning Units”, measured by the equation  PSI x GPM, or as “Cleaning Units/hr”: PSI x GPM x hrs. You will find these numbers in the product literature of a pressure washer and it will give you a good idea of the effective cleaning power of a pressure washer.

While this information can provide a starting point, three important items are left out: heat, nozzle type, and chemicals. Depending on how they combine, they can multiply cleaning effectiveness several times over. Because there is not a standard that considers all five factors, only the professionals at an experienced power wash dealer, like Powerwash.com, can show you the full range of the cleaning capability of a system. This article contains brief explanations of the following topics.

Water Pressure - PSI
Gallons per Minute - GPM
Wands and Nozzles
Nozzle spray-angle applications
Water: the Universal Solvent

Water Pressure - PSI

Water pressure from the pressure washer is measured in pounds per square inch or PSI. This pressure is the amount of force delivered to the surface being cleaned, and is the critical factor in breaking debris from the surface being cleaned. PSI is determined by orifice size of the nozzle tip and the flow rate (gallons per minute). For labeling purposes, the standard nozzle size for measurement is a #4 orifice. This size delivers 0.4/gpm at 40psi and 4.0/gpm at 4,000psi. As nozzle sizes increase or decrease, PSI fluctuates accordingly.  A nozzle chart is necessary in order to determine PSI with different flow rates and nozzles sizes. Nozzle selection depends on the work being done and the amount of pressure the surface can withstand before it is damaged.While PSI is a constant at the tip of the nozzle, the pressure decreases as the distance from the targeted surface increases. Experienced power wash contractors understand how to manipulate these distances for maximum cleaning power and use of time.

3,000 to 3,500 PSI power wash systems are the standard equipment in the contract power washing industry. A big reason for this is that while there is not much of a price difference between 2,000 PSI and 3,000 PSI washers, there is a tremendous difference in cleaning power.

Gallons per Minute - GPM

Gallons per Minute (GPM or g/m) refers to the rate at which water flows from a pressure washer to the surface being cleaned (known as flow rate). Higher GPM improves cleaning ability. Most commercial contractors use a flow rate of 4gpm or greater, because rates below this do not provide a sufficient flow to be able to clean efficiently. Commercial pressure washers typically deliver 4 to 6gpm.  While flow rates less than may do a good job, it is ultimately more expensive as it takes longer, which in turn increases labor costs.

Heat increases the cleaning abilities of water, detergent, chemicals, and solvents. In cleaning applications where grease, oil, and gum are involved heat, manifesting itself as hot water, breaks down these substances quickly, allowing the other products to work at peak efficiency.
Wands and Nozzles

Wands attach to the pressure hose with a gun, the trigger of which starts and stops the flow of water. There are variable pressure wands, dual-lance wands, standard wands, or straight-through wands available.  The one to select depends on the job. Refer to our catalog for complete descriptions of all of our wands. When you call Powerwash.com, we will help you select the right product for your business. Your satisfaction is what matters most.The working end of the wand is fitted with different sized tips or nozzles that provide different spray patterns. Spray patterns range from zero to 65 degrees.  All power washing nozzles have a four or five-digit code stamped on them identifying the spray angle and orifice size. The first two digits refer to the spray (dispersal) angle in degrees:  15 is 15 degrees, 25 is 25 degrees, and so on. The remaining digits refer to the orifice size, and are standardized in the industry. A three-digit number indicates half sizes.

Nozzle spray-angle applications

Zero-degree nozzle – (code stamp 00) provides a concentrated stream for blasting or gouging away stains. It is excellent for:

  • Cleaning overhead areas and kitchen vents

  • Removing dried and caked material from equipment and vehicles

  • Removing heavy stains and buildup from concrete

  • Removing rust and other types of oxidation

Caution:  Using this nozzle improperly will cause injury and serious damage. It can put a hole in your foot unless the proper footwear is worn.  Also, a zero- degree nozzle will leave chicken tracks (tracers) on the surface being cleaned. Prevent this phenomenon by using a zero- degree turbo) rotating nozzle. A turbo nozzle when moved at the proper rate will leave a clean surface without chicken tracks. If the turbo nozzle is moved too fast, it leaves swirls that look like a stretched out Slinky. Turbo nozzles are available in fixed- degree as well as variable degree nozzles in fixed sizes.

15-degree nozzle – This provides a little wider spray and acts like a scraper. It is well-suited for:

  • Heavy duty scraping of water vehicles and equipment

  • Heavy mildew stain removal

  • Removing rust and other types of oxidation

  • Scraping grease and dirt from different surfaces and paint wood, masonry, and metal

25-degree nozzle – This is an excellent tool for sweeping away dirt and debris. Among its applications are:

  • General cleaning

  • Light mildew stain removal

  • Preparation surfaces for painting

  • Removing bacterial and algae build-up in pools

  • Roof, gutter, and downspout cleaning

40-degree nozzle – This nozzle washes large surface areas quickly. Its best uses are for

  • Light cleaning, washing, and rinsing

  • Washing and rinsing cars, pickups, boats, and other watercraft

  • Cleaning flat surfaces such as roofs, windows, patios, and driveways

65-degree nozzle – This nozzle is a wide spray pattern used mostly in spray bars (a long pipe with several nozzles in it to cover a wide area), to cover a wide area without much power. Its best uses are for:

  • Spray Bars

  • Lightly washing a wide area

  • Chemical Application

  • Water Brooms

Please contact our professional customer service department. We can help you find the right wands and nozzles for your power washing needs. In addition, our catalog provides detailed descriptions of all of our wands and nozzles, as well as describing their most efficient applications.

Knowing what equipment to use for different applications is the first step. A qualified vendor like Powerwash.com, will listen to your needs and show you what options best meet those needs. We will also provide training and on-going customer support.

Water: the Universal Solvent

A few words need to be said about water. Water is the “Universal Solvent”, so called because it dissolves more substances than any other liquid, including acids and bases. Pressure washing enhances the cleaning ability of water by adding:

  • Solvents and Chemicals

  • Heat

  • Abrasion (a combination of pressure, spray angle, rotating nozzles and brushing)

  • Dwell time (the length of time a detergent or solvent sits on the area(s) being cleaned)

The proper combination these enhancers with water, and their correct application, will successfully clean almost anything.


The chemicals, solvents, and detergents used all depend on the surface being cleaned and the dirt being removed. Their proper application increases productivity and decreases labor costs. Using them indiscriminately is a danger to the contractor, the crew, and the environment. Careful reading and following of directions is crucial.When cleaning chemicals are properly combined with flow rate, pressure, nozzle configuration, and heat, cleaning is fast and highly efficient. Manipulating any of these five has an impact on cleaning – either positively or negatively – depending on what was adjusted. Misapplication creates dangerous and toxic situations. When you work with Powerwash.com, you will receive expert guidance and training in the proper use, containment, and disposal of chemicals.

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