Dishwasher Owners!!!! Recently I have been asked, “In your reports, why do you always mention that the dishwasher drain line does not have an air gap?” Here is why AND why everyone should verify correct installation ASAP. (And it likely won’t cost you a dime.) The dirty/grey water from your sink WILL drain into your clean dishwasher. Picture 1 – grey dishwater backing up into the dishwasher. Picture 2 – Less than a year old garbage disposal with an organic buildup flowing back into the dishwasher. Most dishwashers, depending on brand, won’t allow this size of organic material to pass through the screens. So the BLACK material is likely organic material from the sink/garbage disposal. Picture 3 – 10 yr old drain line with NO organic material because of proper installation. Picture 4 – Proper installation of dishwasher drain lines.