On Fri, 10 Oct 2008, "Dave, I can't do that" wrote:
On Oct 8, 1:44 pm, "Artemus" wrote:

from the water heater. When a sensor detected a drop in the hot
line pressure the pump would turn on and pump from the hot line

Hmmm, seems a better system than the current one with timer a timer. I
guess a timer costs less than a flow switch. g

If this was my house with a long-pipe problem, the timer would be a
15-minute wind-up Intermatic. You wake up and start your morning
ritual and allow 5 minutes for the pump to get the hot water to the
far end (without wasting any water down the drain) and then hop in the
nice hot shower.

If you keep the hot water pipes hot all the time with a circulating
pump at the far end, you waste a lot of the energy savings of an
instant water heater - as in, the system isn't supposed to be heating
the water /at all/ except when it is actually being used. Might as
well go back to an old style storage tank heater.

We split the house in two a long time ago, so there's no longer one
big electric water heater (and to raise the stupidity level it was in
the attic...) but two medium sized gas water heaters, one at each end
with fairly short runs.

One has 1 and 1/2 baths, the other has one bath, laundry, laundry
sink, dishwasher and kitchen sink.

First one that dies gets replaced with an instant - the kitchen and
laundry end gets the "large" unit, the 1 and 1/2 bath end can get a
"small". And during the process we can use the shower that still has
hot water, so it doesn't have to be done /right that moment/.

-- Bruce --