How to Find & Fix Water Leaks at Home (Complete Guide)

Water leaks waste an average of 10,000 gallons per household per year, according to the EPA. Worse, many leaks are hidden — inside walls, under slabs, or in crawl spaces — silently causing damage for weeks before you notice. In Los Angeles, where many homes sit on slab foundations with aging copper or galvanized pipes, leak detection and repair is one of the most common plumbing calls.

This guide covers how to find hidden leaks, which ones you can fix yourself, and what professional leak repair costs in LA.

Signs You Have a Water Leak

Don't wait for visible water damage. These early warning signs can catch a leak before it becomes expensive:

• Unexplained increase in your water bill. LADWP bills are bimonthly. If your usage jumped without a lifestyle change, a hidden leak is the most likely cause.
• Water meter keeps running. Turn off every fixture and appliance that uses water, then check your meter. If the dial is still moving, water is going somewhere it shouldn't.
• Musty smell or mold. Persistent mildew odor in a room (especially bathrooms, kitchens, or laundry rooms) often means hidden moisture.
• Warm spots on the floor. A hot water line leak under a slab foundation creates a noticeable warm patch on the floor above it.
• Stained or bubbling walls/ceilings. Yellowish-brown water stains or paint bubbling on walls or ceilings are classic signs of a pipe leak behind the surface.
• Sound of running water when nothing is on. If you hear a faint hissing or running sound with all fixtures off, water is escaping somewhere.
• Foundation cracks or shifting. A slab leak can erode soil under your foundation, causing cracks or uneven floors. This is particularly common in older LA homes.

How to Find a Hidden Leak: The Water Meter Test

This is the simplest and most reliable way to confirm a leak exists:

1. Turn off every faucet, appliance, ice maker, sprinkler, and toilet in your home.
2. Locate your water meter (usually near the curb in front of your house in LA).
3. Record the meter reading or note the position of the flow indicator (small triangle or dial).
4. Wait 1–2 hours without using any water.
5. Check the meter again. If the reading changed or the flow indicator moved, you have a leak.

To determine whether the leak is inside or outside your home: turn off the main shutoff valve (usually near the water heater or where the main line enters the house). If the meter stops moving, the leak is inside. If it keeps moving, the leak is between the meter and your house (the supply line).

Types of Water Leaks and How to Fix Them

Faucet leaks

A dripping faucet wastes 3,000+ gallons per year. The fix depends on the faucet type: compression faucets need new rubber washers ($1 part, 10-minute DIY), while cartridge and ceramic disc faucets need a replacement cartridge ($10–$30). Turn off the water supply under the sink, disassemble the handle, and swap the worn part. YouTube has model-specific tutorials for every faucet brand.

Toilet leaks

Toilets are the #1 source of household leaks. Drop a few drops of food coloring into the tank (not the bowl) and wait 15 minutes without flushing. If color appears in the bowl, the flapper is leaking. Replace it — it's a $5 part and 5-minute fix. See our running toilet repair guide for step-by-step instructions.

Pipe joint leaks

Leaks at pipe connections (under sinks, at water heater fittings, at shut-off valves) can sometimes be fixed by tightening the fitting. If tightening doesn't work, the fitting may need to be disassembled and re-sealed with new Teflon tape or pipe joint compound. This is a DIY fix if you're comfortable with basic plumbing, but call a plumber if the leak is on a gas line or a pressurized supply line.

Supply line leaks

Braided stainless steel supply lines (connecting faucets, toilets, and washing machines to the wall) can fail after 8–12 years. A burst supply line can flood a room in minutes. Replacement is a DIY job ($5–$15 per hose), and you should proactively replace any rubber supply hoses (the old black ones) with braided stainless steel.

Slab leaks

A slab leak is a leak in a water pipe that runs underneath or within a concrete slab foundation. This is a major issue in Los Angeles, where thousands of homes built in the 1950s–1970s have copper supply lines embedded in or under the slab. Over decades, these pipes corrode from contact with the soil and eventually develop pinhole leaks.

Signs of a slab leak:

• Warm spots on the floor (hot water line leak)
• Sound of running water from the floor
• Cracks in the foundation or walls
• Sudden spike in water bills
• Damp carpet or warped flooring with no visible source

Slab leaks cannot be fixed DIY. They require professional leak detection (electronic or acoustic equipment to pinpoint the location without tearing up the floor) followed by one of three repair methods:

• Spot repair: Jack-hammer through the slab to access and fix the specific leak point. Cheapest option ($500–$2,000) but doesn't address other aging pipes.
• Reroute: Abandon the leaking pipe and run a new line through the walls or attic instead of under the slab ($1,500–$4,000). Avoids cutting the slab.
• Full repipe: Replace all under-slab pipes with new lines routed through the attic or walls ($3,500–$15,000). The most expensive option but eliminates future slab leak risk entirely.

For detailed slab leak pricing, see our slab leak repair cost guide for LA.

Water Leak Repair Costs in Los Angeles

For more detail on detection costs, see our leak detection cost guide. For plumbing inspection pricing, see our plumbing inspection cost breakdown.

When to Call a Plumber for a Leak

Handle these yourself:

• Dripping faucet (new washer or cartridge)
• Running toilet (new flapper)
• Replacing old supply hoses
• Tightening a loose fitting that's dripping

Call a plumber for:

• Any leak you can hear but can't see
• Slab leak symptoms (warm floor, unexplained water bill spike)
• Leaks inside walls or ceilings
• Burst pipes or flooding
• Gas line leaks (leave the house and call immediately)
• Any leak involving the main water line

Need help now? Browse verified LA plumbers to find licensed leak repair specialists near you, or see our emergency plumber guide for after-hours situations.

How to Prevent Water Leaks

• Replace rubber supply hoses with braided stainless steel on washing machines, dishwashers, and toilets. Rubber hoses are the #1 cause of catastrophic indoor floods.
• Know where your main shutoff valve is. In an emergency, shutting off the main valve within 60 seconds can prevent thousands of dollars in water damage.
• Get a plumbing inspection if your home is over 25 years old. LA homes from the 1950s–1970s with original copper or galvanized pipes are at elevated risk for hidden leaks. Learn about LA plumbing inspections.
• Flush your water heater annually. Sediment buildup accelerates corrosion and can lead to tank leaks.
• Monitor your water bill. LADWP bills are bimonthly — compare each period to catch usage spikes early.
• Insulate exposed pipes in unheated areas. While LA rarely freezes, cold snaps in the San Fernando Valley and foothills can stress old pipes.