Rural water systems: wells, tanks, pumps and pressure

By The Downspout · Updated Oct 11, 2026 · 12 min read

A rural water system gets water legally, stores it, moves it and pressurizes it. In Sonoma County the state sets water rights and Permit Sonoma controls wells. Most homes use a well pump with a pressure tank, or a pump that fills a high tank so gravity does the rest.

Our take. Test your water, and filter it. Science still has unknowns, and a rural system gives water many places to pick something up: the well, the pipes, tanks and fittings. This is our editorial view, not medical advice. See well water and our filter guide.

Start with the right to the water

The State Water Board says the rules depend on where the water comes from.

Creek, spring or river. You need a water right of some type, even for a small home use. A riparian right belongs to land that touches the water and covers its natural flow. A pre-1914 right needs no permit unless your use has grown since 1914. Otherwise you register a small use or apply for a permit. You also file a Statement of Water Diversion and Use, which records your claim but does not prove the right.
Small domestic registration, for home or livestock use. The Board's page gives limits of 4,500 gallons a day for immediate use and 10 acre-feet a year for pond or reservoir storage. It does not work on streams the Board has declared fully appropriated. Check the Board's page for current terms.
Groundwater from a well. The Board says you get the right by pumping the water and putting it to beneficial use. It cannot issue permits for groundwater, except for subterranean streams in known and definite channels. Whether water under your land counts as a subterranean stream is a legal question, so ask the Division of Water Rights. The county still permits the well itself.

You cannot put a pump in a creek without a water right. Not sure what your parcel has? Ask the Division of Water Rights before you build.

Who is in charge in Sonoma County

No county water board hands out water rights. The State Water Board does that. The county decides whether and how you may drill and use a well.

Permit Sonoma. Issues well permits under County Code Chapter 25B and runs metering, dry weather testing and public trust review, covered below. (707) 565-1900.
Groundwater sustainability agencies. Three basins have their own: Sonoma Valley, Petaluma Valley and Santa Rosa Plain. See who manages groundwater. Check which basin you are over on the water map.
Sonoma Water. Runs the Russian River supply for cities and districts, not private wells. See local water agencies.

The parts, in plain words

Well casing and cap. The sealed pipe and cover that keep surface water and critters out.
Submersible pump. A pump and motor that sit down in the water and push it up.
Check valve. A one-way valve so water does not run back down the well.
Pressure switch. Turns the pump on at low pressure and off at high pressure.
Pressure tank. Holds a cushion of air and some water so the pump does not start every time you open a tap.
Pressure gauge and relief valve. Show the pressure and let it off if it gets too high.
Shutoff valves. Let you isolate one part for repair.
Storage tank and float valve. The float stops the fill when the tank is full.
Booster pump. A second pump that moves water from a tank to the house at good pressure.
Pressure reducing valve. Lowers pressure at the house when a tall drop would make too much.

Layout 1: one pump

The well pump does everything. A pressure tank and switch cycle it. Simple and common, and it works when the well makes enough water for your peak use.

Layout 2: gravity feed

The pump fills a tank on high ground and gravity pushes water down to the house. The tank also stores water, so a slow well can fill it over many hours. If the tank is not high enough, pressure is weak. The rule: 0.433 psi per foot of drop, or 2.31 feet per psi.

Layout 3: two pumps

The well pump fills a storage tank. A second pump pulls from it and builds house pressure. It adds one more thing to maintain, and it gives you stored water if the well pump fails.

One pump or two?

One pump: the well makes plenty and the house is near.
Gravity: the well is slow, you have high ground, and you want stored water.
Two pumps: you want storage but have no hill.

A pump dealer or licensed contractor can confirm what fits your land.

Pressure tank

A.Y. McDonald says to set the tank's air pressure 2 psi below the pump's cut-in. It says a motor of 1.5 horsepower or less should run at least one minute each cycle, and a larger one ideally at least two. Short cycling heats the motor and wears it out.

How much storage?

Storage covers pump failure, slow wells and dry months. Pick the number of days you want to cover. Then find your daily use from a well meter or past bills.

How big a pump?

Three numbers decide it: how much water, how high it must go, and what pressure you want.

Flow. Never pick a pump that moves more than the well makes. Use the yield from the driller's log. In scarce water zones Permit Sonoma requires a dry weather test, so a recent test may exist for your parcel.
Head. Add the depth to the water while pumping, any lift to a tank, the pressure you want in feet (psi times 2.31), and an allowance for pipe friction.
Power. Pump makers publish curves. A dealer reads the curve with your flow and head.

Pipes and valves

Narrow pipe at high flow costs pressure. Friction charts from the pipe maker show the loss for each size and flow. Ask for the numbers instead of guessing a gauge. Put a shutoff valve before and after each major part, and a check valve wherever water should not flow backward.

Sonoma County well rules

These come from Permit Sonoma's own pages. Rules and dates change, so confirm before you act.

Who can apply. The applicant for a well permit must be a well drilling contractor with a valid California C-57 license. Applications follow County Code Chapter 25B. A permit covers one new well.
Water zones. The county maps groundwater availability. Dry weather testing is required for a new or replacement dwelling in scarce water zone 4, and for an accessory dwelling in marginal zone 3 or scarce zone 4. Look up your parcel on the county's groundwater availability map, linked from its dry weather testing page.
Dry weather testing. A pump test during the dry season, usually July 15 to October 1. It must show a sustained yield of one gallon per minute per dwelling. A C-57 driller, a C-61/D-21 pumping contractor, a registered civil engineer or a registered geologist must run it. You cannot do it yourself. It can also be required to meet natural resource or health and safety conditions. Check the page for each year's dates. In 2026, shallow wells and springs closed October 1, and deeper wells ran to October 23.
Public trust review. For well applications after October 4, 2022 inside the county's Public Trust Review Area, the county may review whether the well would hurt streamflow. It focuses on summer and fall flow in streams with salmon and steelhead. Its guidance thresholds are a cumulative flow reduction of 10 percent in Coho streams and 20 percent in steelhead streams. If the project is CEQA exempt or CEQA review is already done, review can take three to six months. The permit is not issued until it is done. Wells for existing land use, zero net increase wells and low water use wells are among the exemptions.
Metering. Wells permitted after October 4, 2022 need a meter, except residential wells serving one parcel that use 2.0 acre-feet a year or less. Owners read the meter monthly and report in January. Depth-to-water monitoring starts above 5.0 acre-feet a year.
Old and unused wells. Defective or unused wells must be properly destroyed.
Pump replacement. Not covered on Permit Sonoma's well pages. Call (707) 565-1900 to ask.

The court case. On December 17, 2024, a court order in Russian Riverkeeper and California Coastkeeper v. County of Sonoma told the county to suspend all non-emergency well permitting over public trust concerns. On March 27, 2025, the Court of Appeal granted the county a temporary stay. The county's page shows nothing newer. A second lawsuit over the amended ordinance is ongoing. Emergency wells still need a permit before drilling. Ask Permit Sonoma whether non-emergency applications are being accepted before you plan a new well.

Test your water: labs and kits

Test at the tap, not only at the well. Tanks, pipes and fittings can add bacteria or metals after the water leaves the ground.

How often. Sonoma County Environmental Health suggests bacteria twice a year and after any flood, and nitrates every five years. Use the well test planner to see what is due.

Bacteria: the county lab. The Sonoma County Public Health Regional Laboratory tests for total coliform and E. coli. It does not test chemicals, metals or minerals.

Pick up a bottle in the lobby at 3313 Chanate Road, Santa Rosa. Only the lab's own bottle is accepted.
Choose a cold tap that represents your supply. Take off the aerator. Run the water 2 to 3 minutes.
Slow the flow. Fill to the 100 mL line. Do not touch the inside of the cap or bottle. Cap it, then shake it 10 to 15 times.
Keep it cold, under 10 degrees C (50 F), and bring it in the same day.
Drop off Monday to Thursday, 8 am to 4 pm. Not Friday, weekends, holidays or the day before a holiday.
The sample cannot be more than 30 hours old. Results take about 24 hours. Call 707-565-4711 for fees.

Chemicals and metals. Use a state certified lab. Our well testing page lists the ones the county names. Ask the lab what bottles and steps it wants.

Home kits. UMass Amherst researchers tested eight kits for iron, copper, manganese and fluoride against lab results. Accuracy varied widely. Kits for one substance were more consistent than kits that test a dozen, and all did worse in real water than in clean lab water. Use a kit as a first cut and a lab to be sure. After a flood or wildfire, use a lab.

A single result is one point in time. Keep each one and compare year to year.

Maintenance

Test on the schedule above.
Watch the gauge. Clicking on and off every few seconds is short cycling.
Check tank air pressure with the tank empty, 2 psi below cut-in.
Work the valves a few times a year so they do not seize.
Disinfect after any work in the well. Permit Sonoma has a form, WLS-011 Disinfecting Wells.
Keep your well log and permit papers together.

Who can help

Look for a C-57 licensed well contractor for the well and pump. For tanks, plumbing and electrical, ask each company which license it holds. Check it on the Contractors State License Board site. We do not rank or recommend companies. Our find a water pro page covers how to choose, and our local agencies page lists who regulates what.

Cost planner

Costs vary a lot by site and year, so we give no averages. Get quotes, enter them here and see the total.

Information only. We are not engineers or contractors. Ask a licensed pro before you build.

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.