Dishwasher Not Draining? Start With the Air Gap and the Loop

Water sitting in the bottom of a dishwasher at the end of a cycle sends most people looking for an appliance repair. Often the appliance is fine and the drain connection is the problem.

Check these first

1. **The garbage disposal knockout plug.** On a new disposal installation, there is a plug in the dishwasher inlet that has to be knocked out. If it was missed, the dishwasher cannot drain at all. This is the single most common cause after a disposal replacement.
2. **The disposal itself.** If the dishwasher drains through it and the disposal is full or clogged, the dishwasher backs up. Run the disposal with cold water and try again.
3. **The high loop or air gap.** The drain hose must rise high under the counter, or pass through an air gap fitting, before dropping to the connection. Without it, sink water can siphon back into the dishwasher and the dishwasher may not drain properly.
4. **The drain hose itself.** Kinked, crushed behind the machine, or clogged with debris.
5. **The dishwasher filter.** Most modern machines have one at the bottom of the tub and it needs cleaning periodically. Plenty of owners do not know it exists.
6. **The sink drain.** If the kitchen sink is slow, the dishwasher shares that problem.

The high loop, explained

The drain hose should be secured up under the countertop before it comes back down to the disposal or drain connection. That loop stops dirty sink water flowing back into the dishwasher.

It is a simple thing, it is frequently missed on installation, and it causes both drainage complaints and the smell people blame on the machine.

The air gap

The small cylinder on the sink deck next to the faucet. It provides a physical break so nothing from the drain can be drawn back into the dishwasher.

If yours is spitting water onto the counter during a cycle, the air gap or the hose downstream of it is blocked. The cap and cover come off and the inside can be cleared.

The smell people blame on the dishwasher

Frequently not the dishwasher. Our guide on kitchen sink smells covers the usual causes, and a missing high loop is one of them — standing water in a low hose loop goes stale.

When it is the appliance

• The pump is audibly not running during the drain portion of the cycle.
• The machine reports a drain error code.
• Everything on the drain side checks out and it still holds water.
• The problem started with no change to the plumbing or the disposal.

If you would rather not crawl under the sink

Drain-side dishwasher problems are quick to diagnose properly, and we would rather check the connection than have you replace a working machine. Call (469) 338-5533.