Rainwater Harvesting: Redwood City vs San Mateo
How do rainwater harvesting rules compare between Redwood City, CA and San Mateo, CA?
Redwood City and San Mateo have similar restriction levels.
Redwood City, CA
San Mateo County
Residential rainwater harvesting is encouraged in unincorporated San Mateo County. Under California's Rainwater Capture Act, rooftop rain barrels and cisterns under 360 gallons for outdoor non-potable use need no state water permit. The Countywide Water Pollution Prevention Program offers rebates of $50-$150 per rain barrel, plus a possible $50 bonus in some areas.
View full Redwood City rules →San Mateo, CA
San Mateo County
Rainwater harvesting is legal and encouraged in San Mateo under California AB 1750. Rain barrels under 5,000 gallons are exempt from building permits. Cal Water may offer rebates. Collected rainwater can be used for irrigation and non-potable purposes.
View full San Mateo rules →Key Facts Comparison
| Fact | Redwood City | San Mateo |
|---|---|---|
| State permit | None for rooftop barrels/cisterns < 360 gal | - |
| Controlling law | CA Water Code 10574 (Rainwater Capture Act) | - |
| County rebate | $50-$150 by capacity (50/100/200+ gal) | - |
| Bonus rebate | +$50 in select cities/districts (max $200) | - |
| Rain garden rebate | $300 add-on | - |
| Application window | Within 90 days of purchase | - |
| Legal Status | - | Legal — AB 1750 |
| Permit Exempt | - | Under 5,000 gallons |
| Approved Uses | - | Irrigation, non-potable |
| Water Provider | - | Cal Water Service |
| Vector Control | - | SM County |
Highlighted rows indicate differences between cities.
Redwood City FAQ
Do I need a permit for a rain barrel in unincorporated San Mateo County?
No state water permit is needed for a rooftop rain barrel or cistern under 360 gallons used for outdoor non-potable purposes. Larger or indoor/potable systems may require County plumbing permits.
Are there rebates for rain barrels?
Yes. The Countywide Water Pollution Prevention Program offers $50-$150 per barrel based on capacity, with a possible $50 bonus in some areas (up to $200), plus a $300 rain garden rebate. Apply within 90 days of purchase.
San Mateo FAQ
Can I collect rainwater in San Mateo?
Yes. AB 1750 allows residential rainwater collection. Rain barrels under 5,000 gallons are exempt from permits.
Are there rebates for rain barrels?
Cal Water Service periodically offers rebates. Check their website for current program availability.
Can I drink collected rainwater?
No. Collected rainwater is approved for non-potable uses only. Treatment would be required for potable use.
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