We are remodeling our kitchen, part of which will be replacing the vinyl flooring. When pulling out the vinyl and 1/4" plywood I found many water stains which appear to have started under my dishwasher.
I've run the dishwasher every day and once was able to get it to leak a small puddle of water. Is there a proper way to determine where the leak is coming from? Is it possible to put some sort of pan under the dishwasher in case this happens in the future?
Several places I can think of, but the best way I can think of to narrow it down is to look for water damage on the dishwasher itself.
Check the seal around the door. In my own kitchen, I'll be gutting and expecting to replace a lot of floor boards myself because the dishwasher feet were adjusted too long and were causing it to be crushed by the counter top. The sides of the dishwasher bowed out, losing the seal with the door gasket, and allowing water to escape.
Check the supply line connections. Look for any signs of moisture at the shutoff and where it connects to the dishwasher.
Check the drain connections, again, at the dishwasher (including around any pump) and where it connects to the DWV system.
If a visual inspection of the dishwasher itself doesn't reveal anything, put a few pieces of newspaper under the dishwasher and run it through a cycle to locate the final spot of the drip (which could travel far from the leak itself). But make sure the newspaper is clear of any electrical connections and stays away from any hot motors (you don't want a short or fire), and take the newspaper out after your test.
One overlooked cause of leaks (often from the bottom center of the door) is the door vent. Counterintuitively, when this vent (see the inside top of the door) becomes plugged with years of slimey goo, it will cause spray water to leak down between the outer (metal) and inner (plastic) door. This vent is usually easily pried out and can be cleaned with warm water and a toothbrush. This is a no-cost repair. (Many $50 gaskets are replaced that don't fix the problem.)
You might follow the drain hose back to it's lowest point as well... it could be that if something in the disposal side of the sink backs up the water a little bit during a drain cycle, overflow water might be dribbling back down the drain hose to it's lowest point, dripping on the floor beneath it. It's easier to check, though, because you can just put a paper towel around the drain hose under your sink to see if it gets wet.
