Swollen cabinet under the sink: repair or replace?

Why a swollen cabinet under sink happens

Cabinet board keeps its shape only while it stays dry. When water reaches a cut edge, a screw hole or a chip in the surface, the board soaks it up, softens and swells. You may only notice it when the base feels spongy or the doors start to rub.

Under the sink, the water usually comes from one of three places:

• A slow drip from a tap connection, a pipe joint or the bottle trap.
• A leaking flexible hose that wets the base each time the tap runs.
• Condensation on cold pipes that drips onto the same spot day after day.

Sink cabinet board swelling is often worse at the back, where the pipes come through and water collects out of sight. Look for dark patches, lifted laminate or a musty smell. If the base is wet again soon after you dry it, follow the kitchen sink leaking underneath guide to trace the source first. If you find no leak, the drips may be condensation: see water under the sink but no leak.

Stop the water first

New board will not last if the leak continues. Empty the cabinet, dry every pipe, joint and hose, and lay paper towels on the base. Run the tap briefly, then see which point turns damp first.

HDB's guide to sinks and wash basins says the common wash trap used for the wash basin and kitchen sink in HDB flats is the bottle trap, and that chokes are caused by solid matter or hardened grease in it. If you have cleared a choke recently, check that the trap is screwed back firmly. HDB also says a tap usually leaks when the washer is worn out, and its first step is to turn off the ball valve below the basin or the stop cock next to the water sub-meter.

For pipe joints, HDB's pipes guide says to check the pipe fittings regularly to ensure that there are no leakages, and to shut the stopcock at the PUB water sub-meter to cut the water supply if there is a leakage. PUB's list of simple plumbing works includes replacing a flexible hose connected to a tap, but a leaking pipe joint is not on that list, so it is work for a PUB Licensed Plumber. If a hose has split, bulged or burst, see the flexible hose burst guide.

Repair or replace: how to judge the damage

Once the leak is fixed and the board has dried, check how far the water has spread. A water damaged kitchen cabinet is not always a write-off: press the base and the lower edges of the sides. Firm board can stay; board that crumbles or dents easily needs replacing.

Where the sides are sound, you can replace cabinet base panels on their own, with cut-outs measured around the pipes. Doors that sag or rub are often a hinge problem, covered in the cabinet hinge repair guide. If the sides have swollen and the doors still will not close after adjusting the hinges, a new unit is the lasting fix.

Handyman or contractor?

The size of the job decides who you need. A single base panel, a hinge refit or a new door is handyman work. A new run of cabinets, a new kitchen counter or a sink replacement is a contractor job.

If the leak has also marked the floor or wall beside the cabinet, plan the wider repair before you book anyone. MyNiceHome says that as a home owner you are responsible for maintaining the fittings and fixtures within your flat, such as the floor and wall finishes and sanitary fittings. If you rent, raise the damage with your landlord before arranging any work.

Cost depends on the job and how much board needs replacing. The handyman vs contractor comparison looks at the two in more detail.

Keep it from happening again

A dry cabinet base is the simplest protection: wipe up water as soon as you see it. HDB's pipes guide notes that leaking pipe joints can come from usage and deterioration over time or when pipes are hit by objects, so keep stored items clear of the pipes.

A tray or waterproof liner under the trap catches small drips before they reach the board. Check the hoses, trap and joints regularly for damp, rust or bulges.

HDB's sinks and wash basins guide gives two maintenance tips: fit a strainer, and avoid discarding oil, food waste or solid items into the sink. Both help keep the bottle trap clear.

Questions