9 Signs of a Hidden Water Leak in Your Bathroom

A hidden water leak in your bathroom can cause serious plumbing issues and mold if not identified and fixed. In addition to potentially causing expensive damage to the walls or flooring, a water leak can raise your water bill. But don’t stress—there are some telltale signs you may have a leak, so you can hire a plumber to take care of it before things get worse.

1. Musty Smell

Have you noticed an earthy or musty smell in your bathroom lately, even after giving it a good cleaning? Don’t ignore this crucial sign of a potential water leak. (Or worse, simply try to cover it up with flowery air fresheners.) Keep looking for the hidden water leak, from inside your cabinets to behind your faucet, until you find the source.

2. Mildew or Mold

Mold thrives in moist, dark areas. Pipes, which are hidden in a wall or under flooring, provide the perfect breeding ground. If you see mold or have an allergic reaction, like irritated eyes or wheezy breath, it’s possible you may have a hidden water leak. Investigate further and make sure to clean mold thoroughly so it doesn’t spread.

Keep in mind that it’s normal for a little mildew to occur wherever water accumulates, such as in the corner of a shower. However, mold or mildew on non-shower walls or in corners of the bathroom is a clear sign that water is leaking somewhere and finding its way to those areas.

3. Damaged Paint or Wallpaper

If you see blistering paint or water stains on your pretty wallpaper, you could have a leak in the bathroom. Look at the floorboards, too. Some are like sponges and a little water damage will cause them to expand and warp quickly.

In most cases, steam from hot showers shouldn't cause paint to bubble or wallpaper to peel away. When water and moisture get between the wall and the paint, they weaken the stickiness. You might notice paint beginning to fall off in pieces or wallpaper coming loose. It’s possible to temporarily fix a pipe until you find a plumbing pro who can get there. 

4. Damaged Walls

Another sign of a hidden bathroom leak is wall damage. When the drywall is exposed to moisture, it becomes soft and begins to bubble. Eventually, it will warp and break into pieces. To fix the leak, a plumber often must tear out the drywall, requiring someone to patch and paint when the plumber is finished. If it’s a bad leak, you’ll want to contact a local emergency plumber right away.

5. Wetness in the Cabinet

The only things you want hidden in your bathroom cabinet are extra rolls of toilet paper and cleaning products. But finding water or moisture in there is a sign of a hidden leak. It might be an easy fix, like tightening a nut, but it could also be a sign a valve needs replacing.

6. Damaged Flooring

If your bathroom floor is buckling, cracking, or beginning to stain—and you didn’t let the bathtub overflow—odds are you have a leak. In this case, there could be a leak under your bathroom floor from a concealed pipe, or the water could have traveled there from another area.

You might notice the floor feels soft or spongy. You might even be able to pick up a tile right off the floor. Either way, it needs to be fixed to prevent any further damage.

7. Rocking Toilet

A toilet should feel stable. If it starts to feel like a rocking horse, the wax ring that keeps a water-tight seal between the base and the pipe below could be worn. If you don't already see wastewater on the floor (and the foul smell to match), it’s likely only a matter of time before your toilet leaks from the base. 

8. Loose Faucet

If the bathroom faucet is loose in your hand, water can seep into the gaps. To fix the issue, it might be as easy as applying new caulking to make it watertight again. Of course, a professional plumber can help diagnose the problem to ensure the leak is fixed properly.

9. Stains on Ceilings

If you have a bathroom on the second floor, check the patch of ceiling in the room directly beneath it for stains and signs of water damage. However, because water can travel a long distance, it's possible to find water stains on the ceiling further away.

An occasional wet floor in a second-story bathroom won't cause enough seepage to damage anything underneath it. But any brown, copper, or dark stain on the ceiling is a sign of a water leak in the ceiling. A sagging ceiling is a sign that water from a leak is reaching the area.

Found a Bathroom Water Leak? Here’s What You Should Do

Any sign of water where there should be none is something to address ASAP. Knowing where to look (or smell) can help you catch hidden leaks early and prevent damage. Once you’ve found the source of the bathroom water leak, do the following:

• Shut off the water to the faulty pipes or appliances.

• Clear out any belongings that could get water damage.

• Check for mold.

• Document the damage by taking photos or videos and writing down any key details.

• Read the fine print of your insurance plan to see if your homeowners insurance covers water damage.

• File a water leak insurance claim.

• Repair the leak.

How to Know You Need to Hire a Pro to Fix the Bathroom Leak 

It’s a good idea to call a plumbing repair pro near you when you see signs of a water leak in your bathroom—especially if that leak is more than a dripping faucet and could lead to significant water damage. It can be difficult to find hidden water leaks on your own, and they could have a complex cause. A plumber can find the source, assess the level of damage, and make the most appropriate repair without the guesswork of a DIY.

Can I Repair the Leak Myself?

Some homeowners with plumbing experience may be able to make minor repairs, like fixing damaged caulk or replacing a leaky P-trap, but don’t attempt a DIY unless you’re totally comfortable. You could end up spending more on water damage than you would on a professional repair in the first place. If you suspect a leak in a bathroom wall or see water under the bathroom floor, leave it to the pros. 

How to Prevent Bathroom Leaks 

If you see water under your bathroom floor, it’s already too late. Life happens and pipes do eventually wear down and can spring a leak. The best course of action to fix serious leaks is to prevent them from happening in the first place. Here are some ways you can prevent issues before they begin:

• Inspect your plumbing system for worn-down pipes, fixtures, and connections.

• Replace corroded or aging pipes before they spring a leak.

• Regularly check your caulk and grout for damage and make repairs when necessary.

• Upgrade plastic water supply lines to stainless steel.

• Make prompt repairs when you notice problems before they turn into a leak.

• Use a strainer and regularly clean your drains to prevent clogs.

• Do not flush anything but toilet paper down your toilet.

• Invest in a smart leak detector.

• Address small water leaks before they become big problems.

How Much Does It Cost to Repair Leaks?

The average bathroom leak repair costs $275, but most jobs range from $150 to $600. If you have a complex repair, like a burst pipe, you could spend up to $4,000. Water damage restoration is one of the most costly parts of the job at an average of $3,900. You’ll spend between $4 and $7 per square foot for the water cleanup, plus the cost of drywall, flooring, or fixtures you need to replace.