Copper Heat Recovery Coils
These copper heat recovery coils (picture attached) are required in all new homes now where I live.
They circle the cold water entering a hot water tank around a portion of the drain pipe from the main shower in the residence, so that the fresh water entering the tank absorbs some of the heat of the waste water from a shower as it's draining, saving energy for heating the fresh water.
When I did my last level of plumbing school, we did the calculations for recovering the costs of the coil with the savings in heat energy, and it worked out for a family of four that the cost of the coil would be recovered after 3 - 4 years of use, on average.
From an environmental perspective though, I'm left to wonder if all the costs related to the mining of this copper and the manufacture of the coil have been included in these calculations. Copper is a finite, diminishing resource, is this really the best use of it, to recover a bit of waste heat from shower water? It could be, I just wonder. Especially where I live in Manitoba, Canada, most of the hot water tanks use hydro electric (though there are still quite a few using natural gas) - though I know from this forum, that if we use less electricity in MB, it can be sold into the U.S., reducing the amount of fossil fuels burned there to generate electricity.
On the other hand, thinking about the salvage economy envisioned by JMG, maybe these heavy copper coils are a good idea? Basically they use a good chunk of copper mined when the economy allows for such things, and sits it in houses to be recovered in some future time when it's needed to be melted down from scrap, and the drain easily replaced with plastic or cast iron pipe... Sort of a materials savings account spread throughout the community... (!)