Water leak? The first 48 hours, before mold and insurance problems start

There's a brown ring spreading across the ceiling, a steady drip on the hallway floor, or water running out of a light fixture. Whatever the source, the next two days decide how much gets ruined and whether your insurer pays for it. Water works slowly: it soaks into plaster and subfloor, wicks up the walls, and if things stay wet past a day or two, it starts growing mold.

Below is the order to work in, written for San Francisco houses and stacked flats, with the line between renters, owners and condo associations. For a damp room with no active leak, the mold and condensation guide is the better fit.

#The first 48 hours, hour by hour

1. First 15 minutes

   Stop the water, then think about power

   Close the valve nearest the leak: under the sink, behind the toilet, behind the washer. If water is coming out of a wall or ceiling and there is no valve to close, shut the main. In San Francisco it is usually outside or just inside the house, in line with the water meter at the sidewalk; a gate valve turns clockwise until it stops. Leave the meter box alone, which SFPUC reserves for its own field staff. Then the power. Ready.gov's rule is never to touch electrical equipment that is wet or while you stand in water, and to turn the electricity off only if it is safe to do so. If the panel is across a wet floor, stay out and call 911, then PG&E. Not sure where your valves are? Find them before you need them.

2. 15 to 60 minutes

   Contain it, then photograph it

   Buckets under every drip, rugs rolled up, electronics, books and photos carried to a dry room. Before you mop, shoot photos and video of everything: the ceiling, the floor, the source, and damaged belongings with brands and model numbers showing, the list the Department of Insurance's claims guide asks you to build. If the water is coming from upstairs, knock on that door or call the building manager now. Every minute the valve upstairs stays open adds to the damage and to the argument afterward.

3. First few hours

   Make the calls, and put them in writing

   Report the damage to your insurer; CDI's guide says to report any water damage claim immediately. Renters: call the landlord or manager, then follow up by email so the notice has a date on it. Condo owners: call the HOA manager too, because pipes in the common area are usually the association's. Book a plumber if the water came from a pipe, drain or appliance, or a roofer if it is coming through the roof in a storm. Start a claim diary with every call, name and promise, and the time of each.

4. First day

   Temporary repairs and the first drying

   Cover what's open: plastic over a broken window, a tarp over furniture under a drip. CDI warns that a policy may not cover further damage if you didn't take reasonable steps to protect the property, says the insurer reimburses reasonable protection costs if you save the receipts, and cautions against contractors who push big spending on temporary work. Then move air: fans across wet surfaces, a dehumidifier running with the room's door shut, wet rugs and pads lifted so air reaches both sides. Open windows only when the air outside is drier than the air in.

5. 24 to 48 hours

   Beat the mold clock

   This is the window that matters. EPA says that when wet materials are dried within 24 to 48 hours of a leak, mold won't grow in most cases. Not everything makes it: California's health department tells owners to remove and replace carpet, flooring and building materials that got wet and can't be thoroughly dried within a day (CDPH). Soaked carpet pad and the insulation above a ceiling are the usual losses. Bag them and keep a cut sample, because CDI's guide says not to throw out damaged items until the adjuster tells you to. Email the adjuster early to ask, so nobody lives with wet carpet for a week.

6. After 48 hours

   Repair in the right order

   Fix the source, confirm the materials are dry, then close up ceilings and walls, paint, and do floors last. Don't start permanent repairs until the adjuster has seen the damage. Get at least one written estimate to compare with the insurer's, ask for a complete copy of your policy, which CDI says the insurer must send free within 30 days of your request, and check a contractor's license before you sign. If more damage turns up later, report it right away; CDI notes that a claim can usually be reopened.

#When the ceiling bulges

A ceiling holding water sags before it lets go. Drywall bellies like a water balloon; the lath-and-plaster ceilings in older San Francisco houses are heavier and can come down in slabs. Keep people and pets out from under any sag, and move what you can.

A small bubble in drywall, away from any light or fan, can be drained on purpose. From a steady stepladder, with a bucket below, make a small hole at the lowest point with a screwdriver so the water leaves where you choose instead of all at once. Skip it if the sag is wide, if the ceiling is plaster, if anything electrical is close, or if you would be standing in water. That ceiling waits for whoever repairs it, once the leak is stopped.

#Finding where it's really coming from

Water rarely drips straight down from a leak. It runs along a joist or a pipe and falls at the first low point, often a light fixture, a seam or a corner, sometimes several feet away. Timing gives it away faster than searching does:

• Only when someone upstairs showers or flushes: a drain, the shower pan, the toilet's seal, or failed grout and caulk.
• All the time, even at 3 in the morning: a pressurized supply line, which won't stop on its own.
• Only when it rains: roofing, flashing, a parapet drain, a window frame or cracked stucco.
• Only when the washer, dishwasher or water heater runs: that appliance, its hose or its drain line.

Can't find it at all? SFPUC's Leak Alert program reviews hourly readings from meters that report electronically and, for small properties, flags 48 hours of continuous use at 7.5 gallons an hour or more. Its Customer Services line, (415) 551-3000, can also send someone out to help you locate the main shutoff.

#Neighbor, landlord or HOA: who answers for what

General information, not legal advice. In a building of stacked flats, every leak raises the same two questions: whose pipe, and whose fault?

Renting. California's habitability law puts plumbing “maintained in good working order” and effective waterproofing of the roof and outside walls on the landlord's side (Civil Code 1941.1). Report the leak in writing. Your belongings are another matter: CDI's homeowners and renters guide says plainly that your landlord does not provide insurance for your personal property. That is what renter's insurance is for.

Owning a condo. Unless the declaration says otherwise, the association repairs, replaces and maintains the common area, and each owner maintains their own unit (Civil Code 4775). CDI's guide explains the insurance side: the association's policy generally covers the structure and common areas, while a unit-owner's policy covers the interior and the improvements you're responsible for, and can include loss assessment coverage.

Water from a neighbor. Under Civil Code 1714, everyone is responsible for injury caused by a lack of ordinary care in managing their property. A tub left running is one thing; a pipe that splits inside a wall with no warning may be another. Either way, report to your own insurer promptly instead of waiting on the neighbor's. In a two-unit building or a tenancy in common with no association, the owners' agreement and each owner's policy usually do the sorting, so read yours before the next leak.

• Your insurer

  Report water damage promptly. If a claim stalls, CDI's consumer hotline is 800-927-4357.

  Open the official page

• A plumber

  Supply lines, drains, toilets and water heaters: anything that leaks when the weather is dry.

  Read more

• A roofer

  Water that comes in only when it rains, through the roof or a parapet.

  Read more

• 311 for SFPUC

  A water or sewer emergency in San Francisco: 311, or (415) 701-2311 from outside the city, at any hour.

  Open the official page

• 911, then PG&E

  Water in the electrical panel, sparks, or a gas smell. Get out first and call from outside.

  Open the official page

• Landlord or HOA

  Renters and condo owners: in writing, with photos, as soon as you've called anyone else.

#Insurance: document first, clean second

Most claim trouble after a leak starts with one of three things: damage nobody photographed, belongings thrown out before the adjuster saw them, or a slow leak that went unreported for months.

Disagree with the settlement? Write to the claims manager first, with copies of your documents. California's Fair Claims Settlement Practices Regulations set deadlines for insurers and require any denial to be in writing with reasons, and the Department of Insurance takes requests for help at 800-927-4357.

#Ceilings, walls and floors once it's dry

Repairs go top down once the source is fixed and a moisture reading says dry: ceiling, then walls, then floors. Drywall that stayed soft, sagged or stained through gets cut back to sound board and patched; old plaster may need a section rebuilt, and gouged or swollen walls are wall damage repair. A stain-blocking primer goes on before the paint, or the brown ring bleeds through again. Hardwood that cupped often flattens as it dries, so give it time before deciding on flooring repair.

#Rain leaks are their own job

A storm leak doesn't stop at a valve, and this winter may test plenty of roofs: on September 10, 2026, NOAA's Climate Prediction Center put the chance of a very strong El Niño this fall and winter above 90 percent. Catch the water inside, protect what's under it, and photograph the stain after each storm. Stay off a wet roof. Roofing belongs to a C-39 roofer, the CSLB class for contractors who seal, waterproof and weatherproof structures; water coming in sideways through stucco or around windows is a waterproofing job. The rainy season checklist covers prevention.