Domestic water wheels

I wonder how much electricity you would generate if you connect a small hydro electric power generator to your tap? Would it be better for the environment? It would probably be cheaper, unless you have a water meter. It seems a bit wasteful for the water companies to clean all that water and pump it to your house only for you to leave your tap running to power a light bulb or two.

Maybe its possible to have small hydro electric power generators on all your waste pipes? The problem being they could get clogged up easily unless they were cleverly designed. Maybe a wrap of tiny water wheels around the down pipe may do it. Small turbines on your heating system could get some energy back? Small turbines on your pipes before the water exits your taps my be beneficial, but may tempt people to leave their taps running?