Whatever things are true, whatever things are noble, whatever things are just, whatever things are pure, whatever things are lovely, whatever things are of good report, if there is any virtue and if there is anything praiseworthy -- meditate on these things.
Our new house has fairly long hot water lines to the kitchen and bathroom, so I was looking for different solutions to getting there to be hot water quicker. I researched some tankless heaters, and for the kitchen and washing machine (on one trunk) a small heater (12 amps) would have worked well. But, for the bathroom, a good sized heater (with our 45 degree incoming cold water) would have needed a 200 amp service to the house, with 60 amps (220 volt) dedicated to it. So, an awful lot of upgrades, not counting the tons of ongoing electricity.So, I bought a hot water recirculator at Home Depot, but it turns out it is junk. I talked to a sales guy at the manufacturer, and he didn't seem to understand the problem. The idea is that it watches the temperature of the water in the hot water pipe right under the sink, and whenever it falls under a certain temperature (and also within certain configurable times during the day), it sends the warm water back down to the hot water heater to be reheated. So, the same water is reheated multiple times, using more energy, but you gain time by not waiting for the hot water to be hot, and also not putting all the cold water down the drain. I am not sure how much extra energy is used in reheating the water all the time.
But, the way this particular recirculator works is by putting the warm water into the cold water pipe, on its way down to the heater. So, now you waste warm water and time as you wait for the cold water to cool down. As far as I can figure out, the time wasted is just about the same, though I could route the cold water pipe a shorter distance, and, you are now putting warm water down the drain instead of cold water.
The sales guy agreed that "potentially" that could happen. I don't see how it is not guaranteed for it to waste hot water and time. So, I'll add it to the pile of things to return to home depot - we seem to do that quite often these days.
There are recirculators that use a third pipe, which Watts Premier doesn't sell, presumably why the sales guy had such a hard time admitting their product's weaknesses. (I am sure it would work quite nicely for heating up the hot water pipe quickly)