Dishwasher leak: hidden water damage and what to do

Why dishwasher leaks are easy to miss

A dishwasher sits in a tight space under the counter with cabinets on both sides. A leak at the back or underneath runs into the dark gap beneath the cabinets, called the toe-kick space, and spreads under the kitchen floor. Nothing shows in the room until the flooring swells, a cabinet base softens, or a stain appears on the ceiling downstairs.

Slow leaks can go on for months. Sudden ones, such as a failed supply line, flood the kitchen in minutes.

Signs to watch for

• Water on the floor in front of the machine after a cycle
• Flooring that is lifting, cupping or soft near the dishwasher
• A musty smell from the cabinet beside it or under the sink
• Swollen or peeling cabinet bases and toe-kicks
• Warped or discoloured cabinet sides
• A stain on the ceiling of the room below the kitchen
• Mold along the bottom of adjoining cabinets

Stop it

1. Switch off the dishwasher’s breaker.
2. Close the dishwasher supply valve, usually under the kitchen sink on the hot water line.
3. If you cannot find it, shut the main valve.
4. Mop up visible water.

Common causes

• The supply line. A braided or plastic line from under the sink, or its fittings. A failure here is under constant pressure.
• The drain hose. Split, kinked, or loose at the sink drain or garburator connection.
• The door gasket. Worn or dirty, letting water out at the bottom of the door.
• The pump or motor seals underneath.
• The tub itself, corroded through on an old machine.
• The float or inlet valve, letting the machine overfill.
• The wrong detergent. Ordinary dish soap creates suds that pour out of the door.
• A machine that is not level, so water collects at one side.

Checking for hidden damage

• Remove the toe-kick panel below the dishwasher and look underneath with a flashlight
• Pull off the toe-kick of the cabinets either side
• Empty the sink cabinet and inspect its floor and back
• Press on the floor around the area. Soft spots mean wet subfloor.
• Look at the ceiling below
• Use a moisture meter on cabinet sides, the floor and the wall behind

What gets damaged

Flooring. Hardwood cups, laminate swells, and water spreads under vinyl and tile. Floors often continue under the cabinets, so the damage does too.

Subfloor. Plywood and oriented strand board swell and delaminate when wet for long.

Cabinets. Most cabinet boxes are particleboard or MDF with a thin surface. The bottom edges swell when wet and do not recover. Solid wood face frames and doors usually survive.

The wall behind. Drywall wicks water up and can grow mold behind the cabinets.

The ceiling below, in a two-storey house.

How it is dried

1. The dishwasher is pulled out.
2. Toe-kicks are removed to open the space under the cabinets.
3. Air is directed under the cabinets and into wall cavities, with dehumidification.
4. Flooring that is trapping water is lifted.
5. Readings are taken until everything is back to normal.

Where the cabinet bases are swollen, or mold is growing behind or under them, the affected cabinets have to be removed to reach the wall and floor. That can mean lifting the countertop.

The countertop and matching problem

Replacing one or two base cabinets is rarely simple. A stone or solid-surface countertop may have to be removed and can break. Cabinet styles and finishes are often discontinued. Raise matching with your adjuster early, because it affects how much of the kitchen the repair has to include.

Insurance

A sudden failure is commonly covered for the resulting damage. A leak that has clearly gone on for a long time may be treated as gradual damage. Good photographs of the failed part and the hidden damage, taken before repairs, help show what happened.

Prevention

• Replace the supply line with a braided stainless steel one, and check the connections yearly
• Look under the sink and behind the toe-kick now and then
• Clean the door gasket and the filter
• Run the dishwasher only when someone is home
• Put a leak sensor under the sink and in the toe-kick space

Fridges and other kitchen sources

The same hidden damage comes from other kitchen appliances. A refrigerator with an ice maker or water dispenser is fed by a thin supply line that can split or come loose behind the unit. Under-sink water filters, garburators, instant hot water taps and the sink’s own supply lines and drain all leak into the cabinet base. When you find water damage in a kitchen, check each of these before assuming it was the dishwasher.

Before the new dishwasher goes in

• Make sure the floor, the cabinet sides and the wall behind are dry by meter reading
• Replace the supply line and the drain hose, not just the appliance
• Check that the drain hose has a high loop or an air gap, so that sink water cannot run back into the machine
• Level the machine and fix it to the counter or cabinets
• Run a full cycle with the toe-kick panel off and look underneath with a flashlight

More: water damage restoration.