I am wondering if prolonged cold spells substantially reduce the temperature
of the water entering a house from the city water service . . .

.. . . and if that's true, does that temperature drop translate into
increased stress on water heaters? My neighbor's just failed and last week
we had a water main rupture, too. I can't help but wonder if these are
temperature-related failures.

How would you go about measuring the inlet temperature of water? My thought
is to let the cold water run for about 3 minutes to "cold soak" the pipes
(copper, in my case, uninsulated, too) and then measure the temperature at
the tap.

Letting it run for 3 minutes produced 41.5F on two different digital
thermometers so I guess the answer to my question is that yes, the inlet
temperature varies based on the outside temps and quite a bit more than I
would have imagined. FWIW, it's about 29F outside and has been fairly cold
out for a few weeks.

I'd like to be able to monitor and log the inlet temperature, but it would
be hard to automate a 3 minute "cold soak" measurement like the one I just
took. I have a HomeVision home automation controller that would allow me to
attach a TI digital sensor to the inlet pipe where it enters the house in
the basement. I can log those temps to the PC but it would be a)
"contaminated" by the room heat and b) would vary substantially based on how
much water is or isn't flowing past the external sensor. I suppose I can
discard all but the lowest reading and perhaps put some insulation over the
sensor and around the pipe to reduce the effects of room heat on the sensor.

Thanks for your input in advance . . .

--
Bobby G.