By design, a dishwasher is meant to fill with water, run its wash cycle, and then drain away all remaining water. While your dishes may come out moist if you don’t use a heated dry cycle, there should be no water left in your dishwasher. However, if you come back well after a cycle has finished and you find water at the bottom of the dishwasher tub, then you have a problem.
If water is in your dishwasher when you are not using it, there are two potential issues that could be causing it. The first and most common issue is that there is a problem with the drain. What is essentially happening is that the drained wash water is back flowing into the appliance. This can contaminate your dishes and needs to be dealt with. If you suspect this problem, you will want to make sure the drain hose doesn’t have any potential kinks in it that will impede flow. You will also want to make sure it has the proper alignment to it. If the drain hose is twisted up or laying flat, then that position is not conducive to proper drainage.
The next culprit to consider is the check valve on your sink. This is meant to prevent water that is going down the drain in your sink from being able to flow into your dishwasher through that connected drain. However, if the valve goes bad, then it could fail to perform this function. As such, when you turn on the sink, you may notice that water flows into your dishwasher. This is a pretty easy issue to test as you merely need to turn on your sink and just watch. Water will eventually begin to bubble up from the drain area as if it flows down the drain hose.