Dishwasher doesn't drain fully

[nuxda1963]

I replaced my Kenmore dishwasher with a new Frigidaire. It does not drain properly, leaving about 1.5 gallons in bottom. The drain hose is looped properly and connected to exisiting sink drain connection, per instructions. Is an air gap the only solution? Does it have to be drilled through the countertop? Other options? Thanks.

[DIY Guy]

Since the dishwasher is new, I suspect the problem lies in your drain. Anywhere between where the new hose connects and the open drain, their may be a constriction reducing the flow rate. I'd replace any old hoses/pipes that are still in use.

I don't think the lack of air gap is causing the problem, but it certainly can cause other problems. It is best practice to install a air gap in line from the dishwasher to your home's drain.