I'm contemplating putting in a tankless water heater and have read the
many discussions in this group closely. There is one issue that I
haven't seen discussed, though.
As I understand it, a tankless unit needs to sense a minimum flow for
a second or two before turning on/heating up. So if you are standing
at the kitchen sink washing pots and run the water repeatedly for 5
seconds at time, do you end up getting an alternating flow of hot and
If this is a real problem, would using a very small (2 gallons?) tank
after the tankless unit fix this? Would it have other benefits?
Would this tank need to have an electric heater on it?
Hmmmm. Can't say I've ever noticed this effect. I think between the facts
that (1) there is a significant amount of hot water stored in the water pipes
and (2) the heat exchanger in the water heater doesn't cool down
instantaneously, the "lukewarm" phase isn't really noticeable. The initial
delay to get the first hot water sure is noticeable, 'tho.
On the propane powered one that we use for camping,
what you get is a short burst of warm water that's
already fed into the pipe, followed by a slug of
really hot(*) water that was sitting in the heat
exchanger, a short burst of cool water thats what
fed through before the burner turns on, and then
a continuous stream of warm water.
(*) Never hot enough to actually scald, but
certainly enough to get your attention.
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