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Can you use dish soap in a pressure washer?
Updated
The makers say no. Sun Joe's support page says to use only detergents made for pressure washers and to avoid household detergents, acids, alkaline solutions, bleach, solvents and flammable liquids, since these can damage the machine. Generac's nozzle guide says the same for its soap tip: only power washer safe soaps.
Why dish soap is a bad fit
- The maker says it can harm the machine. Sun Joe groups household detergents with bleach and solvents as things that could damage the pressure washer.
- It is made for a sink, not a siphon. Dish soap is thick and made to foam in a basin. The soap tank and siphon are sized for thin pressure washer detergent, so dish soap may not draw evenly.
- Warranty. Using a cleaner the manual rules out gives the maker a reason to question a claim on the pump or seals.
What to use instead
| Job | Use |
|---|---|
| Cars | A car wash soap labeled for pressure washers or foam cannons |
| Siding, decks, fences | A house and deck wash labeled for pressure washers |
| Driveways, oil spots | A pressure washer degreaser or concrete cleaner |
Kärcher's FAQ says its soaps have no minimum PSI or GPM and work with other brands' quick-connect foam nozzles, so a small machine can still lay down soap. Follow the mix ratio on your bottle. As one example, Sun Joe's guide for its own concentrates gives 1 cup of detergent per 10 cups of water.
How to apply soap
- Fit the soap tip (usually black). Soap will not siphon through a high pressure tip on most machines.
- Apply from the bottom up on walls so it does not streak.
- Let it sit a few minutes. Do not let it dry in the sun.
- Switch to a cleaning tip and rinse from the top down.
- After the job, run clean water through the soap line so nothing dries inside.
Soap tanks on our picks
- Sun Joe SPX3000: two 0.9 liter tanks, so you can keep car soap in one and house wash in the other. The catch is mixed owner reports on long term durability.
- Karcher K1700: a 0.5 gallon detergent tank, the largest here. The catch is no 25 or 40 degree tip listed.
- Westinghouse ePX3100v: a detachable foam cannon, the thickest foam option for cars. The catch is lower rated pressure for other jobs.
Check any listing's numbers with the cleaning units calculator, or see all five machines on our picks page.
Never mix cleaners, and never put bleach or acid in the soap tank. Wear eye protection when you spray soap. It stings.