Dishwasher repair - it is a plumbing appliance

What is dishwasher repair?

Think of a dishwasher as plumbing with a heater in it. The two complaints people bring are it will not drain and it will not clean, and they share almost nothing. Draining is the sump filter, the drain hose, the air gap, the disposal connection and the pump. Cleaning is spray arms, water temperature at the tap, loading and detergent. Diagnosing one while describing the other is how people end up paying for parts they did not need.

Signs you need dishwasher repair

• A few inches of dirty water sitting in the bottom of the tub at the end of every cycle
• Water bubbling or spitting out of the little chrome cylinder on the sink deck during the drain
• The machine was installed recently and has never drained properly since day one
• Dishes come out gritty or with dried food welded on, particularly on the top rack
• Glassware comes out cloudy or filmed, and it does not wipe off
• Water on the floor in front of the door, or a damp cabinet base you only noticed when something warped

Seeing something not on this list? Browse appliance repair problems by symptom →

How dishwasher repair actually works

1. 1

   Establishing whether the fault is inside the machine at all

   The first thing to establish on a drainage complaint is where the water stops. The sump filter at the base of the tub, the drain hose behind the cabinet, the air gap on the sink deck, and the connection into the garbage disposal or the waste tee are all outside the pump. Any one of them can hold water in the tub while the machine itself is perfectly healthy.

   Watch forA drain pump quoted before the filter has been lifted out and looked at. On many machines that filter twists out by hand in seconds and is full of debris.

2. 2

   The knockout plug - the fault that only affects new installs

   Where a dishwasher drains into a garbage disposal, the disposal ships with a solid plug moulded into the dishwasher inlet. It has to be knocked out during installation. When it is not, the dishwasher can never drain, from the very first cycle. This is a five-minute correction that gets misdiagnosed as a failed pump often enough to be worth checking before anything else on a recently installed machine.

   Watch forA brand-new dishwasher that has never drained properly. That is an installation defect, not an appliance fault, and it may be the installer's responsibility rather than yours.

3. 3

   The air gap, the high loop, and backflow

   The drain hose has to rise above the flood level of the sink so waste water cannot siphon back into the tub - either through an air-gap fitting on the sink deck or a high loop secured under the counter. When the air gap clogs, water sprays out of it onto the counter. When there is no loop and no gap, sink water finds its way into the dishwasher.

   Watch forWater appearing in the tub when you run the sink or the disposal. That is backflow from a missing high loop, and no part inside the dishwasher will fix it.

4. 4

   Poor cleaning, which is a different machine problem entirely

   If the machine drains fine but dishes come out dirty, the questions are whether the spray arms turn freely and their holes are clear, whether the filter is choked, whether tall items are blocking the upper arm, and how hot the water arriving at the machine actually is. Wash performance depends heavily on inlet temperature, so a long pipe run from the water heater matters more than most people expect.

   Watch forCloudy glassware being treated as a fault. Hard-water film and etching are water-chemistry problems that respond to rinse aid and a softener, not to replacement parts.

5. 5

   Leaks, separated by where the water actually comes from

   Where it leaks tells the technician what it is. Water at the base of the door usually means a perished or displaced door gasket, a warped door, or overfoaming from the wrong detergent. Water under the cabinet with the machine idle points at the supply connection or the inlet valve. Water only during the wash points at the sump seal, a hose clamp, or the pump housing.

   Watch forA slow leak found only after the cabinet floor or the flooring has swollen. Anything under the machine is worth pulling forward and looking at properly rather than mopping.

What does dishwasher repair cost?

Clearing a filter, an air gap or a knockout plug is at the bottom of the scale and is sometimes not chargeable beyond the visit. Drain pumps, inlet valves and door gaskets are modest parts. Control boards and full pump assemblies are where the arithmetic turns. Ask if the diagnostic is credited when you approve the work.

See the full dishwasher repair cost guide - by material, size and region →

If the number is the problem, here are the ways people pay for it →