Basically, to get rid of the water, the diswasher has to pump it upwards, over the top of a U-bend, where it joins the waste pipe from the sink above the sink’s U-bend. That means that the dishwasher has to put the waste water under some pressure, and this pressure happens to be strong enough to lift the plug of the sink out, even when there is a full sink of water on top of it. There will be a theoretical limit to how high up you can put the waste pipe – my hunch is with this model it is much higher than it needs to be.
Not a major problem, just one of those things that gets on your nerves sometimes. Like tonight.
We’ve had our dishwasher for a couple of years, acquiring it after the one we inherited with the house went out with a bang (and shot sparks the entire length of the kitchen.) It’s a nice dishwasher – that is, it washes dishes nicely, but it’s got an annoying habit that I have just experienced for about the zillionth time. If I’ve got the kitchen sink full of water, and the dishwasher reaches a stage in its cycle where it pumps its water out, it pops the plug out of the sink and I lose my water. (The old dishwasher did this occasionally – the new one does it every time.)