Ah yes. And there's perpetual motion.

I don't think I want to slow the flow. . .

I'm pretty sure there's enough pressure in the lines, especially if you use limited flow faucets/showerheads. This would be the source of the converted energy; it would't just pop out of nowhere, sand.

There is not enough power in the flowing water a household uses to be capturable for domestic use to noticably cut down on the electric bill, and still provide useable flow of the water. An its not free energy, it costs energy to pump that water into your house, and might increase your waterbill due to increased pumping costs by your water utility.

The point is not to recapture the energy for household power, rather for the recirculator itself. The recirculator just pumps cooled water in the hot water line into the cold water line. Its source of power would be waterflow (mechanical energy converted and stored) from normal faucet use, rather than the electrical outlet.

How about recapture on the downstream side instead of the upstream side? I probably wouldn't put a device on my toilet, but a turbine under the kitchen sink would sure get alot of spin action... <tg>

This might work, but it would slow the flow of the water to some degree and the amount of electrical power used by the standard recirculator is too small to be of any real significance. I think the tiny amount of electricity this would save would not make up for the annoyance of the reduction in water flow.

Oh, and putting a turbine in your drain would produce a trivial amount of power and would greatly increase the frequency of clogging the drain.

nayhem: Excellent Idea
Although I do not presently see a practical use for minimizing energy usage in hot water recirculators, I do see a use for generating a small amount of electrical power for the remote control of remote sense water meters and the associated cutoff valve like you have in most homes.

The turbine could produce a small charging current to charge a high value capacitor or long-life rechargeable battery. The remote control circuitry would be driven by the charge off the capacitor and a pilot controlled valve could be manipulated by the control circuit to open and close the main valve. This would eliminate the need for external power so the unit could be wireless.

Excellent Idea

The payback period (where the cost of the unit, labor to install it, upkeep = the savings) would be decades not just years as in hotwater solar panels or wind generators. Now if you were a city like Vegas putting a water turbine deep in the canyon and feed waste water thru it would pay foor itself in just a few years.

I saw a system once that used a venturi on the intake of the tank and a bimetal valve at the end of the line. The valve would open at the specified temperature and the venruri would create a vacuum to draw the water through the return. Only 1 moving part and no electricity.

Tankless water heaters make a lot more sense though.