The short answer
Common Causes
A slow drip from the drain trap or supply lines is a frequent culprit. Water can travel along the pipe and soak the cabinet base without you seeing a puddle. Check the area under the sink for damp spots, water stains, or a swollen cabinet floor.
Condensation is another cause. Cold water pipes running through a warm cabinet can form moisture on the outside, especially in humid weather. That moisture drips onto stored items or the cabinet surfaces, and the dampness turns musty over time.
- Look for water stains on the cabinet floor or walls
- Feel pipes and the drain trap for dampness
- Check for a loose or cracked drain gasket
- Inspect stored items like cleaning supplies for wet bottoms
- Notice a lingering musty smell even after wiping surfaces
Find the Source
Start by emptying the cabinet completely and drying the interior with a cloth. Then run water in the sink for a minute while you watch the pipes below. If you see drips or feel moisture, the leak is likely in the drain or supply connections.
Also turn the shutoff valves under the sink slightly and check for leaks around the valve stems. A slow weep from a valve can go unnoticed for weeks. If you cannot find the source, a plumber can help pinpoint the problem.
- Run water and watch the trap and supply lines
- Turn shutoff valves and check for drips
- Use a dry towel to wipe pipes and see if they stay dry
- Look for dark stains or soft wood that indicate long-term moisture
Dry Out the Cabinet
Once you fix any leak, dry the cabinet thoroughly. Leave the doors open for a day or two and use a fan to circulate air. Remove any wet cardboard boxes or paper bags, as they hold moisture and feed mold growth.
For stubborn dampness, place a moisture absorber or a container of baking soda inside, but remember that these are temporary fixes. The real solution is to eliminate the water source. If the cabinet wood is already soft or blackened, it may need replacement.
- Open cabinet doors and let air circulate
- Wipe all surfaces with a dry cloth
- Remove any wet or damaged items
- Use a fan to speed up drying
- Consider a moisture absorber for ongoing humidity
Clean and Deodorize
After the cabinet is dry, clean the interior with a mild detergent and water. For musty smells, a solution of white vinegar and water can help neutralize odors. Avoid harsh chemicals that might damage the cabinet finish.
If mold is visible on the wood or walls, you may need a mold professional. Mold can spread beyond what you see, especially in porous materials. They can assess the extent and recommend safe removal.
- Mix one part white vinegar with one part water
- Wipe down all surfaces, including corners
- Let the cabinet air out completely before closing
- If mold covers a large area, call a mold professional
When to Call the Pros
If the leak has caused significant water damage to the cabinet, drywall, or flooring, local water damage pros can help. They can assess the extent of moisture and handle drying and repairs that are beyond a simple fix.
Extensive mold growth also warrants professional help. Mold can affect indoor air quality, and some people are sensitive to it. See a doctor if you feel unwell from the smell or exposure.
- If the cabinet floor is soft or sagging
- If you see mold spreading to walls or floors
- If the musty smell persists after cleaning and drying
- If you suspect a hidden leak behind the wall
Water damage does not wait
Phones are answered 24/7 for Mesa and nearby communities.
Call Now (480) 898-4279Frequently asked questions
How long does it take for mold to grow after a leak?
Mold can start growing within 24 to 48 hours in damp conditions. The dark, humid space under a sink is ideal. Acting quickly to dry the area and fix leaks is the right way to prevent mold from taking hold.
Can I just paint over the musty smell?
Painting over a musty smell does not solve the problem. The moisture source must be fixed first. If mold is present, painting over it can trap moisture and allow the mold to continue growing underneath. Clean and dry thoroughly before any paint.
Is a musty smell a sign of a serious problem?
It can be. A musty smell often indicates a slow leak or ongoing moisture, which can lead to wood rot and structural damage over time. It is worth investigating early to avoid more extensive repairs. If you cannot find the source, a plumber can help.