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Old 03-01-16, 07:44 AM   #7
jeff5may
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The most efficient implementation of this strategy is to preheat incoming potable water supply on its way to the water heater. To account for time lag (as with clothes or dish washing), it is more effective to wrap a "worm" tube around the drain pipe section. The longer the length of time the water spends in the worm, the better the usage vs discharge lag is dealt with.

The other common method is to preheat the cold line of a sink or shower with the drain water at its point of use. There have been many builds documented where the shower floor was embedded with hydronic tubing, warming the incoming water with the shower drain water. Some were constructed the same as heating slabs,and some had intimate, direct contact between the drain water and the incoming tubing. Both methods worked well enough to notice the preheating effect.
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