How to Detect Water Leaks in the Wall

Damaged plumbing is often the cause of water leaks, but it can also be caused by rainwater running down inside walls, or by cracked and open foundations. Long-term water infiltration can damage the internal structure of walls and lead to serious mold problems. You can detect water leaks by looking for signs of water damage such as peeling paint or wallpaper, or patchy discoloration of walls. A musty smell in your home can also be a sign of water seeping in. Determine the exact location of the leak by using a water meter or wall cutter.

Table of Contents

Identify water leaks in the wall

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Look for puddles of standing water near walls. This is the simplest way to know if there is a leak in the wall. You can be sure that there is a leak if you find that the carpet is suspiciously wet or the floor is consistently wet in some area of your home. ^{[1] X Research Source}

You will often find wet floors near areas where water-using appliances (washing machines, dishwashers) or in bathrooms near sinks, toilets, or showers.

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Notice the color changing walls. If there is water leaking in the wall, gradually the outside of the wall will change color. Look for walls that are slightly faded or lighter in color than the surrounding area, whether it’s wallpaper, plaster, or even wood.

Patches of color often have no definite shape.

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Observe the change in wall surface texture. Walls with water leaking behind often appear like bubble-like blisters. Paint or wallpaper will shrink or sag, forming tears or blisters as water damages their normal texture. ^{[2] X Research Source}

Drywall with standing water will sag. Small bubbles or wall buckling can also be a sign of water in the wall. ^{[3] X Research Sources}
Walls that are heavily waterlogged can also bend outwards. Drywall will eventually sag because of the weight of the water it contains.

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Watch for signs of mold. If the leak persists for a while, mold can develop inside the wall and on the wall surface. In the early stages, mold looks like black or brown spots concentrated in dense clusters. ^{[4] X Research Source} Even if you can’t see it, mold can still grow inside walls that are soaked by leaks. ^{[5] X Research Sources}

Mold can cause allergies and lead to other serious health problems. If you see mold growing on the wall, remove the mold and repair the leaks in the wall.

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Pay attention to the musty smell. In case the water is not clearly seen behind the wall, you can detect it by smell. The water in the wall has no chance to dry, so the wall will start to smell musty. ^{[6] X Research Sources}

Walls with a musty smell will often be accompanied by other signs of leakage (such as discoloration), but this is not always the case; sometimes a musty smell is the only sign that water has penetrated deep into the wall.
Drywall can absorb water very well (almost like a sponge) making the signs of water leakage not obvious.

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Hear the sound of dripping water. Even if there is no obvious damage, you can still detect a water leak. Listen attentively for the first few seconds after turning off the shower, flushing the toilet, or turning off the faucet in the sink. If you hear a very small trickle of water coming from a nearby wall, it may be caused by a leaky pipe. ^{[7] X Research Sources}

New style water pipes made of PVC will amplify the sound when water is dripping so it is easier to hear. If your home has old-fashioned iron pipes, it will be harder for you to hear.

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Pay attention to the water bill. If the water seeps into the wall quite a bit, you’ll see an increase in your monthly water usage. For example, the US Environmental Protection Agency says a family of four typically uses no more than 45,000 liters a month during the cold months. If you use more than this and don’t know why, it’s probably a water leak. ^{[8] X Research Sources}

Of course, this doesn’t tell you where the leak is, but it at least tells you that there’s a leak in the wall.

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Determine if the water leak is caused by a damaged water line. Turn off all faucets and water-using appliances in your home and record the number on the water meter. Three hours later, check the water meter again: if the number displayed on the meter increases, it means the pipe in your house has a leak. ^{[9] X Research Source}

If the reading on the water meter does not change within 3 hours, it means that the water infiltration is not caused by the pipe. Maybe water drips down from the roof, down the wall, or seeps through the basement walls.

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Check gutters and rainwater pipes. If it isn’t for the pipes, the seepage could be due to clogged gutters and storm drains. Rainwater (or melted snow) with no outlet will eventually seep through roofs and walls. If you find your gutters and storm drains clogged, you need to clear the clog (leaves, etc.) and re-establish the flow. ^{[10] X Research Source}

Even if you don’t see any water seeping into the walls, you should still check your gutters and storm drains every year to make sure they’re not clogged.

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Check for water seeping in the foundation wall. Under favorable conditions, water can seep into the house through the foundation wall. This type of leak is rarely caused by plumbing. Cracked and exposed foundation walls allow water to seep into the walls, eventually starting to drain into the basement. The situation of water leakage in the foundation wall is usually handled in 2 ways: ^{[11] X Research source}

Outside: dig a ditch around the foundation and seal the entire subterranean part of the foundation with a protective sealant or retaining wall.
On the inside: remove damaged columns and drywall, seal cracks with epoxy glue.

Locate the leak

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Detect moisture in the wall with a hygrometer. A hygrometer is a device that is applied directly to the wall to analyze moisture in the wall. If you know there is water in the wall but can’t pinpoint the exact location of the leak, place the hygrometer at 5 or 6 points on the wall. The point with the highest reading is closest to the leak. ^{[12] X Research Source}

You can buy or rent a hygrometer at home repair stores. This device is commonly used by home inspectors to find leaks or damp walls.

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Find cold, water-soaked walls with an infrared camera. The infrared camera detects heat and can tell the temperature of the wall. The water-soaked part of the wall usually has a lower temperature than the surrounding area. Check the camera on the wall that is soaked in water and see which part of the wall is the coldest. That would be the area closest to the leak location. ^{[13] X Research Source}

When viewed with an infrared camera, hot objects will appear red or orange, and cooler objects will appear blue or purple.
You can rent an infrared camera at a home repair center or photo shop.

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Cut drywall to find the source of the leak. Use a multi-purpose knife to make an incision about 25cm long into the drywall at the location where you see signs of water seepage (mold, discolored walls, etc.), then use a saw to cut along the cut line. Cut a hole in the wall wide enough for you to stick your head in. Stick your head into the hole and look around until you find the source of the leak. ^{[14] X Research Source} If needed, you can widen the hole so that a flashlight can be shined in to get a better look at the inside of the wall.

Often the wall that shows signs of water penetration is not directly in front of the leaky pipe. Water can either flow along the outside of the pipe or drip down a great distance and then only meters inside the wall to seep out.
You can buy multi-tools and saws at home improvement stores.

Advice

If you suspect a leak in your wall but can’t pinpoint the exact location, call a plumber or a professional home inspection service to detect the leak. ^{[15] X Research Source}

Steps

Identify water leaks in the wall

Locate the leak

Advice

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