Dripping taps make me mad: both because of their incessant noise and because of the difficulty of cracking open the tap mechanism to fit 5p-worth of replacement rubber washer. Then you strip some threads and it becomes a £200 plumber call-out (cheaper just to sue the tap manufacturer).
When you repeatedly squeeze a rubber washer (especially one in contact with a flow of warm water) it gradually becomes less elastic. This means that people are encouraged to turn the tap further to achieve a seal. Keep this process up and eventually they will graunch an almost inelastic washer between two hard surfaces -and the tap will no longer form a seal. The result will be an incessant drip that you can’t avoid hearing two floors away.
Today’s invention is a mechanical hard stop which prevents a tap being turned closed so far that the washer is compressed more than required to make a seal. It could be supplied as a simple bolt-on attachment to existing taps (although making it aesthetically pleasing might be a challenge).
This would limit the damage that occurs to washers in this context and prolong their working life. The only downside would be that once a leak does eventually begin (due to degradation of the washer material over time, rather than over-compression) there is no way to just close the tap a bit harder using the absurd mechanical advantage most tap designs provide. It’s then simply time to fit a new washer.