Dishwasher venting problems are usually caused by a clogged vent or drain mechanism. As the dishwasher runs, water flows into the unit through the water supply and back out through the drain. To prevent the water from siphoning out of the unit during the washing cycle, air is vented from the dishwasher as water drains. Dishwasher venting problems cause draining problems and may exhibit a few telltale signs, such as water leaking from the air gap, water dripping around the gaskets that seal the door, drain water backing up into the sink, or ineffective washing.
Clogged Air Gap
Some dishwasher installations feature an air gap, a small protruding cap that sits on top of the counter next to the sink. The air gap is connected to a pipe below the sink cabinet and vents air from the dishwasher. If the air gap is clogged, air is trapped within the unit and water may leak from the air gap. A kinked hose or food debris from the dishwasher lodged within the hose are the culprits. If the hose is severely kinked, it may need to be replaced. Rinsing dirty dishes before loading the dishwasher prevents debris from building up in the pipe.
Clogged High Loop
If the dishwasher does not feature a countertop air gap, the unit features a "high loop." A high loop describes the lengthy loop of drain pipe connecting the dishwasher drain opening to the sink plumbing drain or the garbage disposal, if installed. A high loop uses gravity and water's natural siphoning effect to channel drain water up and out of the dishwasher. The high loop prevents dirty drain water from flowing backward into the dishwasher. If the high loop is clogged or the pipe is kinked or twisted, dishes appear soiled after a full washing load. Pools of dirty water remain on the bottom of the unit's tub.
The Garbage Disposal
A full or plugged garbage disposal may cause venting problems. Water may not drain from the dishwasher or may be diverted up and through the air gap. Running the garbage disposal should clean its tank of food debris. If the garbage disposal is newly installed and the dishwasher is not draining or venting properly, the plug to the disposal may not have been removed properly. The drain line to the dishwasher should be removed, the plug removed or knocked out with a hammer, and the drain line reinstalled.
Some models of dishwashers feature tiny vents that channel in air to equalize air pressure during the wash load and to vent steam during the drying cycle. When clogged, the air has no way to escape and hot air is forced through the rubber gaskets that seal the door. A common sign of a clogged vent is a water leak. Some dishwasher models feature the vents on the sides of the dishwasher door. The vents may become coated with grime, food debris or other particles that block air flow. These vents should be regularly checked. To prevent vent problems, dishes should be rinsed of food particles prior to loading the dishwasher.