What can you put in a pressure washer to clean a house?
For a San Diego house you put a sodium hypochlorite mix at 1 to 2 percent, a surfactant to help it cling, and water. That combination kills algae and mildew at low pressure. Straight bleach, concrete degreasers, and dish soap either damage plants or run off before they do anything.
Last updated: July 2026
Most people ask this after they buy or rent a machine and stare at the empty detergent tank. We get the call once the DIY pass leaves streaks or kills a strip of lawn.
The mix we actually run
On stucco and painted siding we soft wash. We drop the pressure to 100 to 150 PSI and let chemistry do the work.
Our house mix is sodium hypochlorite diluted to 1 to 2 percent, plus a surfactant that thickens the solution so it stays on the wall long enough to kill algae. We dwell it eight to ten minutes, then rinse.
And that is it. No blasting the color coat.
What not to pour in the tank
Dish soap does nothing to algae. It just makes suds. Degreasers meant for concrete strip paint off siding. And straight bleach with no surfactant sheets off dry stucco before it can work.
| Cleaner | Works on a house? | Why |
|---|---|---|
| Sodium hypochlorite + surfactant | Yes | Kills algae and mildew, clings to the wall |
| Dish soap | No | Makes suds, does not kill growth |
| Concrete degreaser | No | Too harsh, strips paint |
| Straight bleach | Partly | Runs off before it works, harms plants |
Why San Diego walls grow what they grow
The marine layer is the driver. North-facing and coastal walls in Point Loma, Ocean Beach, and Pacific Beach hold moisture through May Gray and June Gloom, and green algae takes over.
Inland stucco in North Park and Kensington grows more black mildew in the shaded eaves. The same mix handles both.
We pre-wet every plant along the wall and rinse them again after. Sodium hypochlorite at 1 to 2 percent will yellow a hedge if you skip that step.
When to skip the DIY route
A single-story house runs $250 to $500 when we do it, and a two-story $450 to $900. A rented machine plus chemicals runs $80 to $120 for a day, so the savings are real if you have the ladder confidence and the time.
But two-story stucco with north-wall algae is where DIY goes wrong. People reach with high pressure from a ladder, chip the finish, and drive water behind the paper. That repair costs more than the wash.
If your walls are single-story and lightly soiled, the mix above gets you there. Anything higher or heavily grown in, we will soft wash it. See our soft washing and pressure washing pages for how we handle each surface.