Rain barrels, rain gardens and graywater

A typical Palo Alto roof sheds hundreds of gallons in a single good storm. Most of it runs down the driveway, into the gutter and through storm drains to the creeks and the Bay, picking up oil and pet waste on the way. Catching some of that water slows runoff during storms and gives you free irrigation water for the first dry weeks of spring.

The city runs a stormwater rebate program for rain barrels, cisterns and rain gardens. Valley Water pays for simple graywater systems that send washing machine water to the garden. This page lays out both as they were published in fall 2026, with the permit triggers and the practical limits. For flood and storm preparation, see our rain and storm season guide.

The city's stormwater rebates

The City of Palo Alto's Watershed Protection group offers stormwater rebates for residents and businesses. Applications go through Valley Water's Landscape Rebate Program, the same portal used for lawn conversion. These were the published amounts in November 2026:

All of these count toward a combined lifetime cap that also covers the Landscape Conversion and Irrigation Equipment Upgrade rebates. The city lists that cap as $6,000 for single-family and small multifamily sites of four units or fewer and $135,000 for larger sites. If you plan a lawn conversion too, budget the cap across both. Our lawn replacement rebates guide explains the conversion side.

Rules for every stormwater rebate

• Apply first. Equipment bought or installed before you apply is not eligible.
• Owners or tenants with consent. Renters need written consent from the property owner. Contractors may apply for a client.
• Read the city's terms. The city publishes its own terms and conditions alongside Valley Water's requirements.

When you need a permit

Most simple projects need no permit, but the city lists clear triggers. Permit questions go to the Development Center at (650) 329-2496, option 3, which reaches the building plan check team.

• Rain barrels: a permit or consultation is needed for stacked barrels, permanent pumps or plumbing and any connection to drinking water or automatic irrigation.
• Cisterns: needed for below-ground tanks, tanks over 5,000 gallons, pumps, backflow devices or automatic features including irrigation and any connection to drinking water. Submit the permit approval with the rebate application.
• Rain gardens: usually no permit. A grading permit applies only if you move more than 100 cubic yards of soil, far more than a home project needs.

Our building permits guide explains how the Development Center and the online permit portal work.

Making a rain barrel work

A barrel is the cheapest way to start. Put it on a firm, level base under a downspout, raised on blocks so a watering can fits under the spigot. A full 55-gallon barrel weighs about 450 pounds, so the base matters more than people expect.

1. Use a diverter or a screened inlet so leaves and roof grit stay out.
2. Route the overflow away from the foundation, ideally into a planted area or a rain garden.
3. Screen every opening with fine mesh to keep mosquitoes out.
4. Use the water. Drain the barrel onto shrubs between storms so it has room for the next one.
5. Keep it off drinking water lines. Rainwater is for plants, not for the tap.

Be realistic about volume. Palo Alto's rain comes in a handful of winter storms, then none for half the year. A few barrels carry a garden through April and May, not through August. A cistern of 1,000 gallons or more stretches further but costs far more and needs a contractor.

Rain gardens

A rain garden is a shallow planted basin that takes roof water from a downspout and lets it soak into the ground over a day or two. It is the simplest way to keep water on your lot during storms. The plants chosen must handle both soggy winters and dry summers. Valley Water publishes a qualified rain garden plants list and many of the best choices are local natives, covered in our native plants guide.

Siting matters. Keep the basin well away from foundations, avoid spots over septic or utility lines and test drainage first. Dig a hole about a foot deep, fill it with water and see whether it drains within a day. Heavy clay in parts of Palo Alto may need a larger, shallower basin.

Laundry-to-landscape graywater

Graywater is lightly used water from washing machines, showers and bathroom sinks. The simplest legal system in California is laundry-to-landscape: a valve on the washer's drain line sends rinse water through a pipe to mulch basins around trees and shrubs, using only the washer's own pump.

Valley Water's graywater rebate pays $200 in most of the county and $400 to customers of City of Palo Alto Utilities and four other city utilities. The rules as published:

• You must be a homeowner in Santa Clara County with a qualifying property.
• The application must be approved before any work begins. The Notice to Proceed states the mulch basin area you need.
• The system must follow Chapter 15 of the California Plumbing Code, with no filters, tanks or pumps beyond the washer's own pump.
• Mulch basins are required and water may not pool or run off.
• Outlets should sit at least 1.5 feet from property lines and foundations.
• Call 811 before digging.

Valley Water mails the check 4 to 6 weeks after a successful post-inspection. Funding lasts until June 30, 2027 or until depleted. Questions go to the conservation hotline at (408) 630-2554. Valley Water also runs graywater office hour sessions online.

What graywater suits

Fruit trees, large shrubs and perennials do well. Root vegetables and anything eaten raw should not get graywater. Switch to plant-friendly detergents without boron or high salt and send the water back to the sewer when you wash diapers or use bleach.

Which option fits your home

Each approach suits a different kind of property. A rough guide:

• Renters and small yards: one or two rain barrels under a downspout near the patio. They are cheap, portable and need only the owner's written consent for the rebate.
• Ranch houses and Eichlers with long rooflines: a rain garden fed by one or two downspouts. Count the downspouts first, since each one is a possible feed. Our Eichler buying guide covers the roof and drainage quirks of those houses.
• Large lots with fruit trees: laundry-to-landscape graywater gives a steady summer supply every time you do the wash, which barrels cannot match in August.
• Owners planning a big remodel: a cistern is easiest to add while the yard is already torn up and a contractor is on site.

None of these replace good irrigation habits. They work best alongside drip lines, mulch and plants that need little summer water.

Keep mosquitoes out

Standing water is the main worry with any water capture. The Santa Clara County Vector Control District offers free mosquitofish for pools, ponds, fountains and rain barrels. It takes reports of mosquito problems at (408) 918-4770. Our pest and vector control guide covers its other services. A tight lid and fine mesh on every opening do most of the work.

Frequently asked questions