Plumbing Leaks: Causes, Detection & How to Fix Them

What Causes Plumbing Leaks?

Leaks develop for a handful of common reasons, and knowing which one applies often points to where the leak actually is:

• Pipe age and corrosion: older galvanized steel or copper pipes corrode from the inside over decades, eventually developing pinhole leaks
• High water pressure: pressure consistently above the recommended range puts ongoing stress on pipes, joints, and fittings
• Shifting soil or foundation movement: common in California, ground movement can stress pipes running through or under a slab
• Poor original installation: improperly soldered joints or incorrect fittings often fail years after installation, not immediately
• Temperature changes: pipes that expand and contract repeatedly, especially in unconditioned spaces, are more prone to joint failure over time
• Worn seals, washers, and O-rings: the most common cause of fixture leaks (faucets, valves) rather than pipe leaks specifically
• Tree root intrusion: roots seeking moisture can crack or invade underground pipes, particularly older clay or cast iron lines

How to Find a Plumbing Leak in a Slab

Slab leaks (pipes running underneath a concrete foundation) are some of the hardest to spot directly, since the pipe itself is inaccessible. Watch for:

• A noticeable increase in your water bill with no change in usage
• Warm spots on the floor, if the leak is in a hot water line
• The sound of running water when every fixture in the house is off
• Cracks in flooring or baseboards, or damp carpet with no obvious source
• A water meter that keeps moving even with everything shut off

Because the pipe itself is under concrete, confirming and locating a slab leak typically requires professional equipment (acoustic detection or thermal imaging), not something to diagnose with certainty on your own.

How to Find a Leak in Plumbing Pipes Under Floors

Leaks under floors (in a crawl space or between floors, rather than under a slab) tend to show different signs:

• Water stains or discoloration on the ceiling of the room below
• Flooring that feels soft, warped, or springy underfoot
• A persistent musty smell, especially in rooms above a crawl space
• Visible mold or mildew along baseboards
• A drop in water pressure at nearby fixtures

If your home has an accessible crawl space, a visual inspection there can sometimes confirm a leak directly. Where there’s no easy access, the signs above are usually the first clue something needs a closer look.

How to Detect a Plumbing Leak Behind a Wall

Leaks behind walls are often caught later than other types, since there’s no visible pipe and no floor to feel for dampness. Signs to watch for:

• Discoloration, staining, or bubbling paint and wallpaper
• A musty odor concentrated in one area of a room
• The sound of dripping or running water when fixtures are off
• Visible mold, particularly near baseboards or where the wall meets the floor
• An unexplained rise in your water bill

A moisture meter can help narrow down the general area, but confirming the exact location, and repairing it, without unnecessary demolition usually calls for a professional with leak detection equipment.

How to Fix a Leaky Kitchen Faucet

Unlike hidden pipe leaks, a leaky kitchen faucet is one of the few plumbing leaks many homeowners can address themselves:

1. Turn off the water supply valves under the sink before starting any work.
2. Identify your faucet type (compression, ball, cartridge, or ceramic disc), since the fix depends on which one you have.
3. Disassemble the handle carefully, keeping track of screws and small parts.
4. Replace the worn part, usually an O-ring, washer, or cartridge, depending on where the leak is coming from.
5. Reassemble the faucet and turn the water back on, checking for leaks at the handle and base.

If the leak continues after replacing the obvious wear parts, or if you’re not comfortable disassembling the faucet, it’s a quick, inexpensive fix for a licensed plumber rather than something to keep troubleshooting on your own.

When to Call a Professional

• Any suspected slab leak, since confirming location requires specialized equipment
• Leaks behind walls or under floors that would require cutting into drywall or flooring to access
• A faucet repair that doesn’t resolve after replacing standard wear parts
• Any leak accompanied by mold, structural damage, or a rapidly rising water bill

Leak Detection & Repair with Beyond Builder

Beyond Builder provides plumbing services across Los Angeles, Beverly Hills, Bel Air, and the surrounding areas of Southern California, including leak detection and repair for slab leaks, hidden pipe leaks, and fixture repairs. As a licensed general contractor (LIC #1118371), we identify the source of a leak accurately before recommending a repair, so you’re not paying to open up walls or flooring unnecessarily.

Frequently Asked Questions

What causes plumbing leaks most often?

Pipe age and corrosion, high water pressure, shifting soil, and poor original installation are the most common causes, along with worn seals and washers for fixture-specific leaks.

How do I find a plumbing leak in a slab?

Watch for a rising water bill, warm spots on the floor, or the sound of running water with everything off. Confirming the exact location typically requires professional acoustic or thermal detection equipment.

How do I find a leak in plumbing pipes under floors?

Look for water stains on the ceiling below, warped or soft flooring, musty odors, and visible mold near baseboards.

How do I detect a plumbing leak behind a wall?

Watch for discoloration or bubbling paint, a musty smell, the sound of dripping water, and an unexplained increase in your water bill.

How do I fix a leaky kitchen faucet?

Turn off the water supply, identify your faucet type, and replace the worn O-ring, washer, or cartridge. If the leak continues afterward, it’s worth calling a licensed plumber.

Get a Free Leak Detection Quote

Not sure where a leak is coming from? Contact Beyond Builder today for a free, no-obligation quote.