Using Harvested Rainwater for Pressure Washing
Pressure washing uses 2-5 gallons per minute, and a typical session cleaning a driveway, deck, or house siding takes 20-60 minutes, consuming 50-150 gallons of water. Our estimate of 100 gallons reflects a periodic use averaged over regular cleaning intervals. Rainwater works well in pressure washers because its low mineral content means no scale buildup in the pump and nozzle. Soft rainwater also improves cleaning effectiveness, as detergents and surfactants lather more readily without mineral interference. For pressure washing use, a pre-filter is recommended to protect the washer pump from sediment. A dedicated rainwater tank for pressure washing can be relatively small (200-500 gallons) since the use is intermittent. Position the tank near your typical washing areas to minimize hose runs and pressure loss.
Pressure Washing Potential by State
How much of your pressure washing demand can rainwater meet? It depends on where you live. The table below shows the annual harvest, demand coverage, and recommended tank size for pressure washing in eight representative states, using a 1,500-square-foot asphalt shingle roof .
| State | Annual Rainfall | Annual Harvest | Demand Met | Rec. Tank | Savings/Year |
|---|---|---|---|---|---|
| California | 22.2" | 13,756 gal | 37.7% | 55 gal | $123.80 |
| Texas | 28.9" | 22,277 gal | 61.0% | 55 gal | $111.39 |
| Florida | 54.5" | 39,622 gal | 100.0% | 5,000 gal | $182.50 |
| New York | 46.2" | 33,641 gal | 92.2% | 55 gal | $302.77 |
| Colorado | 15.9" | 11,589 gal | 31.8% | 55 gal | $57.95 |
| Hawaii | 63.7" | 45,229 gal | 100.0% | 2,500 gal | $547.50 |
| Arizona | 13.6" | 8,373 gal | 22.9% | 55 gal | $50.24 |
| Washington | 38.4" | 27,511 gal | 75.4% | 1,500 gal | $165.07 |
Setup Requirements for Pressure Washing
Pressure washing with rainwater is an excellent application because the soft, mineral-free water improves cleaning effectiveness while protecting your pressure washer from scale buildup. A pre-filter (100-200 mesh) is recommended to protect the pump from sediment. Since pressure washers use 2-5 gallons per minute, you can go through 50-150 gallons in a single cleaning session — plan your tank capacity accordingly.
A dedicated 200-500 gallon tank near your typical washing areas provides convenient access and adequate supply for most residential cleaning jobs. The tank should be positioned at the same level as or slightly above your pressure washer's inlet for gravity assist. If your tank is lower than the washer, you may need a booster pump to ensure adequate inlet flow to the pressure washer pump — most pressure washers require positive inlet pressure and cannot self-prime from a tank below their level.
Other Rainwater Uses
Explore other ways to use harvested rainwater at home:
- Garden Irrigation — 50 gal/day
- Lawn Irrigation — 75 gal/day
- Toilet Flushing — 20 gal/day
- Laundry — 15 gal/day
- Car Washing — 50 gal/day
- Livestock Watering — 30 gal/day
- Pool Top-Off — 10 gal/day
- Drinking and Cooking — 1 gal/day (potable treatment required)
- General Outdoor Use — 30 gal/day
Calculate Your Pressure Washing Potential
Use our Rainwater Harvesting Calculator to see how much of your pressure washing demand can be met by rainwater in your specific location. Select pressure washing from the use checkboxes along with any other uses you are considering, and get a personalized monthly supply vs. demand analysis with tank size recommendation and cost savings estimate.