Water leak or leaking pipe: what to do first, finding it and cost

For Silicon Valley homes · Updated October 2026 · Sources below

Shut off the water first - at the valve under the fixture, or at the main shutoff for the house. Most leaks come from a supply line, fitting, valve or pipe joint and can be fixed in one visit. Don't let a small leak wait: the EPA says an average home's leaks can waste more than 9,300 gallons a year, and wet materials need to be dried within 24-48 hours to prevent mold.

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Water near outlets, wiring or a sagging ceiling? Turn off the power to that area at the breaker panel, shut off the main water valve and keep people away from the wet area.

The short version

First step: shut off the fixture valve or the home's main water shutoff
Meter test: note your water meter, use no water for 2 hours, check again - any change suggests a leak
An average home's leaks can waste more than 9,300 gallons a year (EPA)
Dry wet drywall, flooring and cabinets within 24-48 hours to prevent mold (EPA)
Stopping a leak usually needs no permit; replacing hidden pipe or repiping does

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What it costs

Repair a leaking pipe$150 - $350, plus about $100 to find it
Patch drywall after the repair$250 - $750

Water damage cleanup is extra if the leak spread.

Typical ranges from published cost guides - mostly national figures. Bay Area prices usually run higher. Your actual price depends on your home and the job, and a pro gives you the real number. Source: HomeAdvisor cost guide (national) (Feb 2022). Have a quote? Check it with the Quote Explainer

Signs of a hidden leak

Your water bill jumps without a change in how you use water
The water meter moves when every tap and appliance is off
Stains, soft spots or bubbling paint on walls or ceilings
A musty smell or mold under a sink or behind a wall
The sound of running water when nothing is on

What to do first

Shut off the water at the fixture valve. If you can't find one, or it won't stop the leak, close the main shutoff for the house.
If water is near outlets, wiring or light fixtures, turn off that circuit at the breaker panel and keep away.
Move belongings out of the way, catch drips and start drying the area.
Take photos and video of the leak and any damage before cleanup, for your insurer.
Call a plumber to find and fix the source, and dry or remove wet materials within 24-48 hours.

In Silicon Valley

Valley Water (Santa Clara County's water district) offers free water-saving devices like WaterSense showerheads and sink aerators, and links leak-detection resources on its water-saving page.
Outdoor leaks count too: the EPA says a 1/32-inch leak in an irrigation system can waste about 6,300 gallons a month. Valley Water offers a free Water Wise Outdoor Survey of your irrigation system.
The California Department of Insurance says one of the most important steps after a loss is making temporary repairs to prevent further damage - a policy may not cover damage that spreads because you didn't.

Questions homeowners ask

How do I know if I have a hidden water leak?

Use your water meter: write down the reading, use no water for two hours, and check again. If it moved, you likely have a leak. The EPA also says a family of four using more than 12,000 gallons a month in winter probably has a serious leak.

What should I do first when a pipe is leaking?

Shut off the water - at the valve under the sink or toilet, or at the main shutoff if the leak is in a wall or ceiling. If water is near anything electrical, turn off that circuit at the panel. Then catch the water, start drying and call a plumber.

Is a water leak an emergency?

Yes, if water is spraying, coming through a ceiling, or near outlets or wiring - shut off the main water and the power to that area and call a plumber right away. A slow drip under a sink can usually wait for a scheduled visit, as long as you catch the water and dry the cabinet.

How much does it cost to fix a leaking pipe?

National cost guides put a pipe leak repair at about $150 to $350, plus about $100 to find a hidden leak, and $250 to $750 to patch drywall afterward. Bay Area prices usually run higher, and water damage cleanup is extra if the leak spread.

How long before a leak causes mold?

The EPA says to dry water-damaged areas and items within 24 to 48 hours to prevent mold growth. If drywall, insulation or carpet stays wet longer, it may need to be removed rather than dried.

Does homeowners insurance cover a leaking pipe?

It depends on your policy. California's Department of Insurance lists water damage among losses a homeowners policy may cover, and says to report the damage to your insurer and make temporary repairs to prevent further damage. Read your policy or ask your agent before major cleanup.

Do I need a permit to fix a leak?

Usually not to stop a leak or replace a supply line. Replacing a hidden pipe, repiping or moving fixtures needs a plumbing permit, which your plumber normally pulls.

Do you need a permit?

Small repairs usually don't; replacing pipes does.

General guidance based on California's building code - your city can have stricter rules, and zoning, historic and HOA rules can apply too. Check with your city's building department before you start.

Check the rule for your city

Questions to ask the pro

How will you find the leak, and does that cost extra?
Is opening and patching the wall or ceiling included?
Is this pipe worth spot-repairing, or is the rest of it near the end too?
Does this repair need a permit?
How long is the repair warrantied?

Before you sign, check the contractor's license at cslb.ca.gov. How to hire a contractor in California

Know a neighbor dealing with this?

Send them this page - it's free, and every answer has its sources.

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