The load of dishes is finished and you open the door to the smell of spoiled food. The entire bottom of the dishwasher is covered in stale, dirty water, and the dishes are covered with chunks of food. You could call a plumber, but that will run you at least £97 for the visit, and most likely the repair will be so simple you will wish you did it yourself. Fixing a non-draining dishwasher is simple and can be accomplished within a two-hour span, saving you money.
Clean the air gap. The air gap is located under the sink and connects to the sink’s drain. Clean it by lifting off the metal cap and unscrewing the plastic cap underneath. It should unscrew by hand. Clean the cap and the two exposed pipes by pouring 1/2 cup of baking soda into the pipes followed by one cup of white distilled vinegar. Replace the cap, and let the pipes bubble for 10 minutes. Run the sink and the dishwasher to check for proper draining.
Check your dishwasher model. If you have a GE or KitchenAid machine, the drain valve solenoid could be malfunctioning. Remove the dishwasher door panel by removing the screws on the top and sides, and review the circuit map to determine the applicable circuit line. Remove those wires from their terminals and clip each wire to a volt ohmmeter. If the needle does not move when you run the meter, the wires are dead. Replace the wires with new ones and run the machine.
Disassemble the pump, and place each piece in a bucket of hot vinegar. Soak the pieces for one hour and wipe off any food and mineral build-up with a rag. Inspect the vanes (small tubes) of the drain pump. The veins should be connected to the pump; if the veins have disconnected, reconnect them onto the impeller and reassemble the cleaned pump.
Contact a plumber who specialises in timers if none of these solutions solve the problem.