I have a friend who works for the NHS. She told me that none of the sinks in hospitals have plugs for infection control. Washing in a sink is carried out by leaving the tap running, which wastes huge ammounts of water (throughout all the hospitals in the UK) and makes it very difficult to control temperature if the sink has separate taps.
I started thinking about making a disposable plug from starch based plastics, until I realised that all I really needed was a disk of card - the waxy variety used for coffee cups. It wouldn't need to be very robust to withstand 15 minutes of one sided immersion, then be pulled out and put in the bin. It would also be very difficult to be used twice, because once water logged it would start to degrade and it would be very cheap to produce. I'm sure the problem and solution is not as simple as a disk of card, but something like this could give greater patient experience and cut down on wasting water.