That wouldn't explain why dishwashers don't have them.
Opening one of them that has broken down full of water isn't much fun either.
Opening one of them that has broken down full of water isn't much fun either.
How does that happen? Every dishwasher I have owned is perfectly safe to open at any point in the wash cycle. Maybe the sensor that detects how much water is in the machine fails and it fills up completely?
As you hint it's a very rare mode of failure, and dishwashers don't use much water — a modern energy-star compliant dishwasher uses about 15L (~4gal) per cycle and the most efficient ones can go lower than 12L (~3.2gal) — so in most cases a blocked drain will end up with visible water staying at the bottom of the dishwasher and may not even overflow it to the door. The drain would need to be blocked directly at the top of the dishwasher drain, and seriously blocked (e.g. your asshole brother plugging it)