In the first installment of our dishwasher series, I said one of the most common dishwasher inspection faults I find in the Houston area are improper drain installation.

Just to review in case you missed it, in most homes, the dishwasher is connected to the food disposal for drainage of waste water. Because there is a direct connection between the food disposer and the dishwasher we must prevent back flow into the dishwasher from the disposal.Houston Home Inspector

Imagine your clean dishes in the dishwasher being exposed to waste from the disposal. The potential for harmful bacteria is significant so we want to do all we can to ensure back flow does not occur.

The air gap is a very effective method for preventing food disposal back flow into the dishwasher. Its name tells you how it works. An air gap is created that prevents the back flow. Air gaps are quite common in plumbing. Every sink faucet utilizes an air gap between the water supply and the drain. The distance from the faucet to the water level in the sink is the “air gap”.

Think of your dish washer drain hose as the “faucet” in this setup.Waste water flowing from your dishwasher flows out the “faucet” side of the air gap into the “sink” side which is the disposal drain.
Harris County Home Inspection

If the disposal pumps water backwards through the air gap, it will spill on the counter just like an overflowing sink. This is why the slot in the sir gap cover should always face towards the sink. If a back flow occurs we want it to go towards the sink and not towards the back splash.

Delta Kitchen Air Gap

© 2018 Patrick Miceli