you can just hook the faucet up to your device, and let the water pressure drive the generator directly. In either case, for a bathtub faucet, this works out to almost 200 watts, or $25 per month
Though what you could do is place small turbines in your piping so that any time you use your water for normal uses, it would generate some electricity at the cost of a loss of pressure once it passes through. Though it would be more efficient to just turn down the pumps generating that pressure to the new pressure setting and using the electricity saved there (if you are the one running the pump, water included in rent would transfer some energy to you but lose some overall).
You didn’t read past the first paragraph.
Though what you could do is place small turbines in your piping so that any time you use your water for normal uses, it would generate some electricity at the cost of a loss of pressure once it passes through. Though it would be more efficient to just turn down the pumps generating that pressure to the new pressure setting and using the electricity saved there (if you are the one running the pump, water included in rent would transfer some energy to you but lose some overall).