Dishwashers fail in fewer ways than most appliances. There's a pump, a heater, a fill valve, a drain pump, a door latch and a control, plus the hoses between them. Most complaints come back to one of those parts or to something simpler: a filter nobody knew existed, a new garbage disposal, a detergent that doesn't suit the water.
Below are the five problems that account for most dishwasher trouble, each with the checks worth trying first. Before any of them, turn off the dishwasher's breaker or unplug it under the sink. If you'll be touching hoses, close the hot-water valve under the sink too.
1. Water sitting in the bottom after the cycle
A little water left in the sump, under the filter, is normal on many models. An inch or more across the tub floor is not.
Check the filter. Most dishwashers built in recent years have a manual filter, usually a cylinder that twists out of the tub floor below the lower spray arm. Food, labels and broken glass collect in it. Twist it out, scrub it under a hot tap with an old toothbrush, and look into the hole beneath for anything lodged there.
Think about the disposal. A brand-new disposal ships with a plastic plug sealing its dishwasher port, and the installer is supposed to knock it out. When that step gets skipped, the dishwasher's drain hose dead-ends. Also run the disposal before starting the dishwasher; a full disposal chamber backs water up.
Check the drain hose and air gap. Under the sink, the hose ought to climb up to a high loop just below the countertop or go to an air gap, the small chrome cap beside the faucet. Air gaps clog. Pop the cover off and clear any gunk.
If all of that is clear and you hear the drain pump hum without moving water, or hear nothing when it should be draining, the pump or its check valve is likely at fault.
2. Leaking onto the floor
Where the water appears helps narrow it down.
- •At the front, under the door. Look at the door gasket for tears or food stuck along it. Check that the dishwasher is level side to side; a tilted tub lets water ride over the door lip. Suds are another cause. Hand dish soap in a dishwasher, or even a bit of it left on pre-rinsed plates, foams up and pushes water out past the seal.
- •Under the unit, toward the back. That's the plumbing: the fill valve connection, the drain hose clamp, or the pump seal. Remove the lower kick panel with a flashlight in hand while a cycle runs and look for drips.
- •Only when the spray arms run. A cracked or warped spray arm can shoot water sideways at the door seams.
Some brands, Bosch among them, have a float switch in the base that shuts the machine down when it senses water, so you'll get an error before you get a puddle. Our Bosch dishwasher guide explains how that works.
3. Nothing happens when you press Start
Before anything else, check whether the control lock is on. Most models have a lock that disables the buttons, often shown by a padlock symbol and set by holding one button for a few seconds. Kids and cleaning cloths set it by accident all the time.
Then look at:
- •The door latch. The dishwasher won't start unless the latch switch senses a closed door. If the door has to be slammed or held to start a cycle, the latch or its strike is worn or out of line.
- •Power. A GFCI outlet under the sink or a tripped breaker. Some dishwashers are hardwired, so check the panel.
- •Delay start. A cycle set to begin hours from now looks exactly like a dead dishwasher.
If the panel lights but nothing runs, or the display is dark with confirmed power, the latch switch, a thermal fuse or the control board is the likely suspect. That's a diagnosis for a technician.
4. Dishes come out dirty
Clean dishes need hot water, enough of it, and spray arms that can spin freely.
- •Run the kitchen tap hot before starting. On a long pipe run, the first minute of water is cold, and the dishwasher's first fill takes it.
- •Spin the spray arms by hand. They should turn freely and nothing tall should block them. Pull them off (most unclip or unscrew) and clear the holes with a toothpick.
- •Clean the filter. A clogged filter sends dirty water back onto the dishes.
- •Load for the spray. Bowls facing in toward the center, nothing nested, big pans at the back or sides of the bottom rack.
If the water in the tub is barely warm halfway through a normal cycle, or the dishwasher runs noticeably shorter than it used to, the heater, its thermostat or the circulation pump may be failing.
5. White film, cloudy glasses or crusty spray arms
WSSC Water, which supplies most homes in Montgomery and Prince George's counties, carries dissolved minerals like any river-fed supply, and over time they deposit inside dishwashers. Mineral scale shows up as a chalky white film on glasses and a crust around spray arm holes and the heating element.
Two things can look the same but aren't:
- •Mineral film wipes off with vinegar. Leave one cloudy glass sitting in plain white vinegar for five minutes. Clear glass afterward means scale.
- •Etching is permanent. The glass surface has been worn by detergent chemistry, often from heavy detergent doses in soft water or from very hot settings. Vinegar does nothing to it.
For scale, keep the rinse aid dispenser filled, use a quality detergent at the dose on the package, and every so often run the machine empty and hot with a descaling cleaner made for dishwashers. Some models have a water hardness setting in the menu. If yours does, WSSC Water publishes its water quality figures, and your manual explains how to match the setting.
When to have it looked at
Call when the drain pump is silent or hums without moving water, when you can't find the source of a leak, when the machine won't start with power and an unlocked panel, or when the water never gets hot. A technician will check the pump, heater, fill valve, latch and control in one visit, and tell you in plain terms what broke and what the fix costs, so you can decide before anything is replaced. If the tub is rusted through or the dishwasher is at the end of its useful life, you'll hear that, and our repair or replace guide can help you weigh it.
To book, call or go through our dishwasher repair page.