Bleach solutions can effectively remove mold and mildew from your house's siding. However, bleach, which has the chemical compound sodium hypochlorite as its active ingredient, is corrosive. Since pressure washers have many metal parts, including the water pump through which most persons siphon bleach solution, and bleach is corrosive, it's important to use a bleach solution in a pressure washer in a conscientious manner. Neglect or indifference to the chemical reaction taking place between the internal metal and rubber parts in the water pump, primarily, and the active ingredient in bleach means the pressure washer will need major service sooner than rather than later. Some pressure washer manufacturers do not suggest using bleach in a pressure washer, and will even void warranties if it is used. Check the product manual for specifications.
Position the pressure washer wherever it will best serve you during cleaning. Place the bucket near the pressure washer.
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Don your protective eyewear and protective gloves.
Mix one part bleach to four parts water in a bucket for medium-level cleaning tasks when the bleach solution is 5.25% to 6%. Mix three parts water to one part bleach in a bucket for medium-level cleaning tasks when the bleach is 3% sodium hypochlorite.
Ensure the siphon hose and filter aren't clogged, and clean them of clogs if necessary. Place the weighted strainer on the end of the siphon tube (the soft pliable PVC tubing that usually fits directly to the water pump on the pressure washer) into the bleach solution in the bucket.
Usage and Cleanup
Connect a water hose to the pressure washer. Connect a soap tip to the pressure washer gun wand or lance. Connect the pressure washer gun to the pressure washer hoses and then attach the pressure washer hoses to the pressure washer.
Turn on water to the pressure washer. Start the pressure washer by pulling the recoil cord or switching on the electric start.
Lower the engine speed to near its lowest speed to reduce water pressure. Turn the pressure adjustment dial to lower water pressure.
Squeeze the pressure washer gun trigger while aiming at whatever it is you're cleaning. The force from the water pressure circulating through the pressure washer will pull the bleach solution up through the siphon hose and further mix it with water and onto whatever it is you're cleaning.
Shut off the pressure washer engine to replenish the bleach solution, if doing so will take more than a few seconds. When you are done, fill the bucket with clear water and run it through the pressure washer to clean out the bleach in the system.