Is your Sonoma County water safe to drink? City, well, tank, creek and rain

By The Downspout · Updated Oct 11, 2026 · 10 min read

City water is disinfected with chlorine, and Sonoma Water and Santa Rosa say they add no fluoride. Wells, tanks, creeks and rain have no one testing them for you. Look up your supplier, then find your source below.

Start here: who sends you water?

Enter your address. We show the supplier on the state map and what we have confirmed from that supplier. If we have not confirmed it, the tool says so.

Enter an address to see who supplies it.

We cannot tell you your water is safe. Only your supplier's own test results show how your water did. Find them in its Consumer Confidence Report. EPA requires one each year.

Our take. Filter your water, wherever you are. Science still has a lot of unknowns. Chlorine byproducts, metals from pipes and tanks, and whatever water picks up on the way to your glass have not all been shown harmless. A certified filter is a cheap way to cut those unknowns. This is our editorial view, not medical advice, and not a claim that your water is unsafe. Filters do not remove everything, so testing still matters. See our guide to water filters.

Jump to your source: city tap, well, storage tank, creek or spring, rain, bottled, fluoride.

Your water report: what it is and where to find it

Every public water supplier must send its customers a yearly water quality report. The official name is the Consumer Confidence Report, or CCR. It is due each year by July 1. We keep saying "your report" below. This is the one.

It lists where your water comes from, which regulated contaminants were found and how much, and whether the system broke any health standard. It has phone numbers for questions.

How to find yours:

Check your water bill and your mail. Many suppliers send or link it there.
Search the web for your supplier's name plus consumer confidence report or water quality report. Use the supplier name the lookup above shows. Your bill names it too.
Use EPA's lookup: search for your local report.
Call the number on your bill and ask for the latest report.

If you read one line, find the disinfection byproduct results (trihalomethanes and haloacetic acids) and any lead or nitrate notes. If your supplier adds fluoride, that result too.

City tap: what is actually in it?

Besides water, mainly a disinfectant, and a pH adjustment.

Chlorine. Sonoma Water adds it to keep the water disinfected throughout its transmission pipe system. Santa Rosa says it uses chlorine too, and that it may leave a bleach smell.
pH adjustment. Sonoma Water adds sodium hydroxide. Its target is a daily average pH of 8.2 to 8.6, for 95 percent of days.

Some suppliers use chloramine, a related disinfectant, instead of chlorine. Your report says which.

How to read a number: parts per million

In water, 1 part per million (ppm) is 1 milligram per liter (mg/L).
That is about one drop in 13 gallons.
Parts per billion (ppb) is 1,000 times smaller. 0.080 mg/L is 80 ppb.
Reports use mg/L, ppm or ppb. Convert before you compare.

Why chlorine, and what does it cost us?

It keeps germs from growing in the pipes between the plant and your tap. That is the case for it.

The cost is byproducts. Chlorine reacts with organic matter in the water and makes trihalomethanes and haloacetic acids. EPA's legal limits are 0.080 mg/L for the first and 0.060 mg/L for the second. It says drinking them above those limits for many years can raise health risks. For trihalomethanes it lists liver, kidney and nervous system problems and a higher cancer risk. For haloacetic acids it lists a higher cancer risk.

How strong is the evidence? A Canadian review by S.E. Hrudey (archived, written in 2008) found that after more than 30 years of research no byproduct at regulated levels had a proven health effect for any specific outcome. It found no causal link between trihalomethanes and bladder cancer, and called the reproductive evidence inconsistent. It still called a causal link a live hypothesis and urged reasonable precaution. It is an older review, and we did not find a newer one that settles it.

What about fluoride?

Sonoma Water and Santa Rosa say they do not add it. We have not confirmed Windsor, Healdsburg or Cloverdale. Check your report.

Many other places do add it. CDC recommends 0.7 mg/L and says it lowers cavities by about 25 percent. A 2024 Cochrane update found the benefit is much smaller in newer studies than in ones from before 1975, and may be nothing.

High levels are known to cause harm. The fight is over levels near 0.7. The US National Toxicology Program has moderate confidence that fluoride above 1.5 mg/L is linked to lower IQ in children, and not enough data at 0.7. A 2019 Canadian study and a 2025 meta-analysis found similar links, but outside experts called the first weak and rated most studies in the second high risk of bias. A federal judge ordered EPA to act in 2024, and an appeals court threw that order out in 2026 without deciding whether the risk is real.

Nobody has settled it at 0.7. Ask your own dentist or doctor. If you want it out, reverse osmosis or distillation removes it. Carbon filters do not.

What tap water has going for it

A public system is tested on a schedule and must publish the results. You can read the numbers yourself, with no lab fee.

Our take: filter city water

Here the reasons are chlorine taste and byproducts, and whatever water picks up in pipes between the plant and your glass. Start with what you want out, not with a product.

Chlorine taste or smell: an activated carbon filter.
Fluoride, if your supplier adds it: reverse osmosis or distillation.
Anything in your report you want lower: match the filter to that item.

Pick a filter certified by a third party such as NSF International. The label should name the contaminants it reduces. Common NSF/ANSI standards are 42 for taste and odor, 53 for health-related contaminants and 58 for reverse osmosis. Change cartridges on the maker's schedule.

Test your own tap

The report is your supplier's testing. A sample from your own tap tests your plumbing too. UMass Amherst researchers advise a first-draw sample, water that sat in the pipes overnight, to check metals from home plumbing. They say to test if your plumbing is about 20 years old or older, or after a flood or wildfire.

The most reliable choice is a state certified lab. Our well testing page lists the ones the county names. Home kits vary widely in accuracy, so treat them as a first cut. For labs, bacteria tests and kits in detail, see testing in our rural water guide.

Well water

No one tests a private well for you. You do. Test first, treat second. Treatment that does not match the problem wastes money. See test your well water and the well test planner. For pumps, tanks and pressure, see our rural water guide.

Alabama Extension lists these matches for common problems:

Treatments can be chained, with a pre-filter, a main unit and a final step. Ask a professional before you pick one, and ask for a certified product. Costs and upkeep are in our filter guide.

Water stored in a tank

Many rural homes store water in a tank. It can come from a well, a spring or a delivery. Stored water can grow algae, collect sediment and pick up bacteria. Sunlight feeds algae, so use a tank that blocks light.

Shasta County Environmental Health says to clean a tank about every 5 years, and every year at startup for a seasonal supply. Clean sooner if you see sediment or growth, after repairs, if coliform bacteria show up, or if the taste, smell or color changes.

Scrub the inside and drain out the dirty water.
Add enough 8.5 percent bleach to reach 10 ppm chlorine and fill the tank. A 5,000 gallon tank takes about 0.6 gallon of bleach. Let it sit 24 hours.
Drain it, not into a septic system. Refill and run the taps until the chlorine smell is gone.
Test for coliform bacteria. A negative result means the water is considered safe to drink.

Keep bottled water on hand while the tank is out of service. To size a tank, use the tank size calculator. For pumps and pressure, see the rural water guide.

Creek, spring or river water

Untreated surface water can carry bacteria, viruses and parasites such as Giardia and Cryptosporidium, from human or animal waste. CDC says clear water can still be unsafe. A spring is not automatically clean.

Boiling kills all of them. Hold a rolling boil for 1 minute, or 3 minutes above 6,500 feet.
Filters with an absolute pore size of 1 micron or smaller, or an NSF 53 or 58 cyst rating, remove parasites. They do not remove viruses. Filter first, then disinfect.
Reverse osmosis removes parasites, bacteria and viruses.

None of this removes chemicals. If you suspect fertilizer, fuel or runoff, test the water at a lab. Taking water from a creek or spring also needs a water right. See water rights in our rural guide.

Rainwater

Rain is good for gardens. For drinking it needs work. Sacramento County Environmental Management calls rainwater from catchment systems non-potable and untested. It can carry bacteria, parasites or chemicals, and bird droppings on the roof add germs.

Collect only from a roof, never from the ground.
Cover every opening with mesh of 1/16 inch or finer, so mosquitoes and rodents stay out.
A first flush diverter throws away the first, dirtiest runoff.
Never connect a rain system to your drinking water without a permit and a backflow device.

To drink it, you would filter, disinfect and test it. Sonoma County rules may differ from Sacramento's, so ask Permit Sonoma before you build. See keeping rain on your land and our rain and storage articles.

Bottled water

If you buy water, it is not a fix. It is a stopgap. A 2024 study in PNAS, by Columbia and Rutgers researchers, found about 240,000 nanoplastic particles per liter in three common brands, from 110,000 to 400,000. The authors said they do not know if it is dangerous. The bottled water industry group says there is no standard way to measure it and no scientific consensus on health effects. Researchers say much of the plastic may come from the bottle and from the filter membrane used in production.

Our view: if you buy plastic, pick BPA-free. That is a place to start, not proof that the plastic is harmless. Store water in glass or stainless steel when you can. Nobody has shown that drinking from plastic is safe over decades, and the research on plastic in food and water is still early.

What we do not know

We did not read every study. We read the main ones named above and what outside experts said about them.
Rain, tank and creek rules are from other counties or national agencies. Sonoma County may differ.
The state boundary map is a 2019 snapshot and may put a street in the wrong district.

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Sources

Checked 2026-10-11. Rules and programs change. If something here is out of date, the source above wins. Spot an error? See our corrections policy.