Why is my water bill so high? How to read a Sonoma County water and sewer bill

By The Downspout · Posted Oct 23, 2026 · 12 min read

Most high bills come from summer watering, a leak, last winter's water use or a rate increase. Compare the units on your bill with the same month last year. If the units went up, check your meter for a leak. In most Sonoma County cities the sewer charge is partly set by how much water you used last winter, so fix leaks before winter.

Listen to this article

Read aloud by an AI voice.

Here is a number that surprises most people. A typical Petaluma home pays about $170 a month for water and sewer. The charge for the water you actually use is about $47 of that.^[1]

The rest pays for pipes, meters and the plant that cleans what goes down the drain. In most Sonoma County cities, sewer is the larger share of the bill.^[2]

We use Petaluma as the worked example because it posts every rate and a sample bill. Your city works the same way, with its own prices. Below: each line on the bill, one unit of water followed from the river to the drain, the usual reasons a bill jumps, a 10-minute leak check, and who sets the rates.

What is on your bill?

Your bill comes from your city or water district. Many of them buy their water from a regional water agency called Sonoma Water, then sell it to you.^[3] Most bills have the same few parts.

Units used. Many utilities here count water in units of 100 cubic feet. The bill may say "hcf" or "ccf". One unit is 748 gallons.^[4] Petaluma's bill shows cubic feet. Divide by 100 to get units.^[5] Sebastopol prices water per 1,000 gallons instead.^[2]
Days in the billing period. Petaluma bills every month.^[6] Sebastopol bills every two months.^[2] Billing periods vary in length. Petaluma's sample bill covers 35 days.^[5] To compare two bills fairly, multiply the units by 748 to get gallons, then divide by the days.
A fixed water charge. You pay it even if you use no water. It is set by the size of your meter. In Petaluma it is $23.37 a month for a standard home meter.^[1] Santa Rosa charges the same way.^[7]
A water use charge. This is the price per unit. For single-family homes it usually comes in tiers: the first units are cheapest, and each tier above costs more. Petaluma has four tiers, from $6.43 to $9.01 a unit.^[1]
A fixed sewer charge. In Petaluma, $45.80 a month for a single-family home.^[1]
A sewer use charge. Nobody meters what goes down your drain. So most cities here estimate it from the water you used last winter, when little water goes on gardens.^[8] More on this below, because it is the part most people miss.

Here is how those parts add up for one Petaluma home at four levels of use. Look at the blue part, sewer. Using more water this month does not raise it, because it is set by last winter. At 4 units it is a little lower, because Petaluma charges your actual use when that is less than your winter average.^[1]

Our calculation from Petaluma's 2026-27 rates. See how we did the math.

Follow one unit of water through the bill

Take one unit, 748 gallons. That would fill thirteen or fourteen 55 gallon rain barrels.

It starts at the Russian River. Sonoma Water pumps it from deep wells next to the river. Big underground pipes, called aqueducts, carry it to towns like Santa Rosa.^[9] Our guide to where your tap water comes from follows that trip.

Wholesale, it costs about half a cent a gallon. That is the price Sonoma Water charges the cities.^[3]^[10] That is about $3.74 for our 748 gallons.

At your meter, it costs roughly double. Petaluma charges $6.43 for the same unit in its first tier, and $9.01 in its top tier.^[1] The difference pays for the city's own pipes, tanks, pumps, testing and staff. That is a lot of pipe, and much of it is old. Santa Rosa, for example, keeps up more than 1,200 miles of water and sewer pipe. Much went in during the 1960s and 70s, and it spends about $30 million a year on fixes and upgrades.^[9]

Down the drain, it costs more again. Most cities here set your sewer charge from the water you use in winter. We explain why below. For each unit of your winter average, Petaluma charges $10.85 a month to take it away and clean it.^[1] Our guide to where wastewater goes shows the plant that does it.

Add it up. Each unit of your winter average costs a Petaluma home about $11 a month in sewer charges, for a full year. That is on top of about $7 for the water itself.

Gravel walkway separating a house wall from a mulched garden bed and green lawn. — A garden bed and lawn beside a house. Outdoor watering is why summer use climbs, and summer is when the higher tier prices kick in.

Why did my water bill go up?

Start by finding the units on this bill and on the same month last year. If the units went up, it is your use. If the units are the same and the dollars went up, it is the rates.

Summer watering

Indoors, a person usually needs 25 to 50 gallons a day.^[5] In summer, use climbs because of outdoor watering.^[5]

Tiers make the extra water cost more. A typical Petaluma home uses about 7 units a month. That reaches the second tier, where each unit costs more.^[1] Water a lawn through July and you can climb into the third or fourth. Your bill or your utility's rate page shows where each tier starts.

The fix is the garden, not the shower. Our guides to lawns and drought tolerant plants show where to start. Most utilities here also pay you to replace a lawn.

A leak

Leaks are common. The average home's leaks waste more than 9,300 gallons a year, about 12 units. About 9% of homes have leaks that waste 50 gallons or more a day.^[11] Worn toilet flappers, dripping faucets and leaking valves are the usual causes.^[11] A broken irrigation line can waste far more: a hole the thickness of a dime can lose about 6,300 gallons a month.^[11]

A 50 gallon a day leak adds about 2 units a month. On Petaluma rates, that is about $15 more on the water side of the bill each month, for a home that uses 7 units.

Last winter's water use

This one surprises people. The sewer use charge is not based on this month. It is based on how much water you used last winter.

Petaluma charges sewer use on your average winter water use, or on your actual use if that is lower. It updates the average each July.^[1]
In Sonoma and much of Sonoma Valley, sewer service comes from the Sonoma Valley County Sanitation District. It bases 30% of a home's sewer bill on water used from December through February. The other 70% is a fixed charge.^[12]
Cotati, Healdsburg, Rohnert Park, Santa Rosa, Sebastopol and Windsor also base sewer charges partly on winter water use.^[8]

The reason: in winter, little water goes on gardens, so the water you use is close to what goes down the drain.^[1] It also means using less water in winter lowers your sewer charge for the whole next year. But it means a winter leak, or watering in a dry winter, costs you all year.

Here is the math. Say that same 50 gallon a day leak runs through the winter in Petaluma. Your winter average goes up by about 2 units. When the city updates your average in July, your sewer charge goes up by about $22 a month for the next 12 months. That is about $260 a year, on top of the water itself. In Sonoma and much of Sonoma Valley, where the sanitation district counts winter water differently, the same leak adds about $145 a year in sewer charges, by the district's own calculator formula.^[8]

So the time to find leaks is now, before the winter months that set your sewer charge. Ask your utility which months it counts.

Rate increases

If your units did not change, the price did. Many cities here, including Petaluma, Santa Rosa and Sebastopol, raise rates every July on a five-year schedule.^[6]^[13]^[2]

Santa Rosa raises sewer rates 5% each July from 2025 through 2029, and water rates 6% a year through 2027, then 7% in 2028 and 2029.^[13]
Petaluma raised most bills about 6% in July 2026.^[6]
Sonoma Water raised the price it charges cities by about 8% to 9% for 2026-27.^[10] Each city decides how much of that to pass on to you.^[10]

Here is how the two parts of a typical bill compared across the county in 2024-25. Look at how often the blue part, sewer, is longer. These are older numbers from a comparison Sebastopol made in 2024, and rates have gone up since. Compare the shape of the bars, not the exact dollars.^[2]

How to check for a leak in 10 minutes

Find your meter. It is usually in a concrete box marked "WATER" near the street or sidewalk. Lift the lid gently with a screwdriver.^[14]
Turn off every tap, sprinkler and appliance. Then watch the small star on the meter face. That is the low-flow indicator. If it spins, water is going somewhere.^[14]
Find out if it is inside or outside. Close your home's main shut-off valve, often near an outdoor faucet where the pipe enters the house. If the indicator stops, the leak is inside. If it keeps spinning, the leak is outside, often the irrigation system or the line from the meter.^[14]
Test each toilet. Put a few drops of food coloring in the tank. If color shows in the bowl within 10 minutes, the flapper leaks. Flush afterward so it does not stain.^[11] Replacing a flapper is a quick and easy fix.^[11]

For slow leaks, read the meter before and after two hours with no water use. Any change probably means a leak.^[11] For a winter check: a family of four that uses more than 12,000 gallons in one month, about 16 units, in January or February may have a serious leak.^[11]

Petaluma customers can sign up for EyeOnWater, a free online account that shows hourly use and sends leak alerts.^[15] Petaluma also offers free Water-Wise HouseCalls, a personal visit to help you use water more efficiently inside and outside your home. Call (707) 778-4507.^[14] For leaks you cannot find or fix, call a licensed plumber. Our guide to finding a licensed water pro shows how to check a license.

Who sets the rates, and can you push back?

Your city council or district board sets them. Proposition 218, a change to the state constitution that voters passed in 1996, limits what they can do.^[2]^[16] Here is what it means for you.

Rates can only cover the cost of the service. Water money can only pay for water, and sewer money for sewer.^[2]^[16]
You usually get a notice in the mail before a rate increase, and there is a public hearing.^[2]
You can protest in writing. Property owners or customers can protest. If more than half of the affected properties protest before the hearing ends, the increase cannot go ahead.^[2]

Watch your mail for that notice. It is the moment your voice counts most.

Why rates rise when we all save water

This is the real tension in water bills. Many of a utility's costs, like replacing pipes, maintenance and staff, stay the same whether you use more water or less.^[1] But much of its money comes from selling water by the unit. When everyone saves, revenue falls, and the price per unit goes up.^[16]

It has happened here. In the drought, cities bought less water, so Sonoma Water sold less. It said that drop cut its savings, its reserves, by $12.8 million over three years.^[17] In 2026 it said lower demand had again reduced its revenue.^[10]

Sebastopol is the sharpest example. Its 2019 rates did not plan for how much people would conserve, so revenue fell short. In July 2024, water and sewer rates rose 37%.^[16] The city said it had used reserves to keep rates down through COVID, and that many parts of its systems were near the end of their life.^[2] A 2026 report by the Sonoma County Civil Grand Jury, a citizen panel that reviews local government, found another cause. For years, the city had billed its water and sewer accounts too much for general city costs. The grand jury put it at about $5.5 million over nine years.^[16]

Does saving water still pay? In 2023, Sonoma Water said it does: by conserving, every customer avoided the cost of finding, delivering and treating new water that would otherwise have been needed.^[18] Customers who cut back, as they were asked to, then saw rates jump. In Sebastopol, citizen complaints led to the grand jury review, and the grand jury said the 37% increase was hard for many customers to accept.^[16]

Our take: saving water still pays you. Your own bill is lower than it would be, and the fixed costs would be there either way. Water you do not use stays in our rivers and aquifers, which fish and people share. The way to keep rates fair is regular rate studies and open hearings, so there are no 37% surprises.

If you cannot pay the bill

Call your utility before the due date. Many offer payment plans. Sebastopol works them out case by case.^[2]

Petaluma has a written policy on shutting off water for unpaid bills, which it adopted to comply with a state law, the Water Shutoff Protection Act. The policy covers payment arrangements and how to dispute a bill.^[6] Ask your utility for its version.

What it means for you

Compare units, not dollars. Same month last year, gallons per day.
Check for leaks this month, before the winter months that set your sewer charge for a year.
Cut outdoor water first. That is where summer tiers bite.
Open the rate notice when it comes. You can comment, and you can protest.

Next: find your supplier on the water map, see what your utility will pay you to save water, or read what is in the water you pay for in our guide to water quality reports.

Photos by Devan Hemmings unless noted.

Sources

Checked 2026-10-23. Rules and programs change. If something here is out of date, the source above wins. Spot an error? See our corrections policy.