Repair costs vary by issue, typically from $100 to $500, depending on the parts needed and labor involved.

A clogged air gap can cause a dishwasher not to drain. There are, however, other potential issues that can lead to improper drainage. For example, if you have attached the air gap to a garbage disposal and forgotten to remove the knockout plug, wastewater may backflow into the dishwasher. Check that the air gap is installed properly, and then look for clogs in the air gap and dishwasher filters. 

When a dishwasher discharges its wastewater, it uses a pump to quickly move a lot of water. If anything in the drain line or the garbage disposal impedes the high volume of water, it will back up into the sink through the drain or the garbage disposal. Following regular dishwasher maintenance tips like clearing clogs, keeping them cleared, and occasionally running the disposal will eliminate the problem.

You should deep-clean your dishwasher every month for optimal performance. A simple scrub down using a homemade vinegar liquid solution is all you need, but don’t use cleaners that aren’t for dishwashers. 

If your dishwasher needs repair, expect to spend between $50 and $100 or $100 to $200 per hour to hire a dishwasher repair technician to service your machine.

Treat hard water with water treatment tablets to keep your dishes from getting spotty in between washes. Drop one of these into your dishwasher monthly and run a basic cycle with the machine empty.