It could be a case of unrealistic expectations, or possibly a flawed plumbing design. In either case, John Metcalfe has discovered that installing a pair of tankless water heaters in his San Francisco house has done anything but solve his hot-water delivery problems.
In a post at GreenBuildingAdvisor’s Q&A Forum, Metcalfe laments that even with the new heaters plus a recirculation pump, there is a two-minute wait for hot water at the kitchen sink or at an upstairs shower. What gives?
Tankless heaters will mean a slightly longer wait than would be the case with a conventional tank heater, says GBA senior editor Martin Holladay, but Metcalfe may see some improvement by making sure the recirculation pump is activated by a switch in the kitchen or bathroom. Moving the heaters closer to where hot water is needed also would help.
Others question a key detail of the plumbing system: the new tankless heaters are connected in series. More than one GBA reader finds the arrangement puzzling.
Metcalfe’s hot-water woes, and some possible solutions, are the focus of this Q&A Spotlight.
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Tankless water heaters eliminate some energy losses, but they don't necessarily make the wait for hot water in the kitchen or shower any shorter.
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I'm sure you've checked this out but I know that if your recirc pump isn't big enough it won't kick the heater on. Therefore you are circulating cold water instead of warm water. Also I've seen putting in a small tank heater in like 5-10gal tank water heater in line with the recirc pump will keep the water warm in the lines but that's less efficient. So I'd try changing the impeller in your recirc pump to push more water and kick the heater on.
I tend to favour the tried and tested methods of plumbing to be honest. Too many variables with a new method that has still yet to be perfected that I'm not willing to adapt it until there are impeccable reviews on how it can work for us!