The only dishwarmer I have used is the Paterson type, of which I have 4 or 5 examples. Essentially it is a rectangular box with a flanged top, the flange of which reaches down the side about 15 mm. This provides protection against splashes but I would not put one of these warmers anywhere near a sink, only on a benchtop where all spillages drain away rapidly. To place the warmer anywhere where it could accidentally get flooded would be far too risky - flooding would ruin the warmer (which is not sealed) and create a lethal shock hazard (an RCD would provide some safety against shock, but flooding would still ruin the device).
Originally Posted by Fintan