Ever wonder where all that energy you consume to heat up your shower water goes? Well, down the proverbial drain. (Never mind that we are bathing in potable water.) The vast majority of those therms are being flushed! Recovering heat from drain water is not a new idea, and some folks out there are commercializing systems to capture some waste-water energy. Take a look at Ecodrain and GFX Technology, for example. Many other home-grown systems are out there – including Continuum’s. For grins, we built up a shower water heat exchanger that preheats the input cold water using the drain water. It’s our newest resident of our shower lab. The preheated water mixes with the hot at the shower valve, hence lowering the flowrate of the expensive and impactful hot water. Save energy, money, and lower CO2 emmissions. We got pretty wet in the process, too.

Quick and dirty results:
Input Cold: 50F
Shower Drain Water: 65F
Cold After Preheating: 64F

Input Cold: 50F
Shower Drain Water: 72F
Cold After Preheating: 68F

Our shower drain water was tepid, at best, because Wednesday was basketball lunch day and the folks here used the hot water – thankfully.

Next installment of the shower heat exchanger: some analysis and more results. (An LCA that considers copper use will come at some point…)