Last year, I've attempted to enter this same project in the Hackaday prize contest, but unfortunately I couldn't put enough time into it due to work and moving to a new location. This time I hope to have the time to complete the project because my wife and I would love to have this luxury in our bathroom! It would make life slightly simpler.
We've just recently finished completely remodelling our bathroom so we thought it would be the perfect time to attempt to implement the system. I still have many of the components from last year so we're already a step ahead.
The biggest challenge that I'm currently facing is to be able to control the bathtub drain electronically. My first thought was to control a valve using a servo, but I haven't found a valve that would be easy to operate using a servo. I've thought of using a stepper motor and gearbox, but I find that to be very loud and annoying. I will continue to experiment and post my results.