"MLD" wrote in message ...
"Robert Green" wrote in message

stuff snipped

. . . and if that's true, does that temperature drop translate into
increased stress on water heaters?

If the water heater has to operate longer to bring the incoming water up
to
temperature translates into " increased stress", then so be it. But
that's
how it is supposed to work.

If NASA had a little foresight about the problems of cold weather, they
might not have dropped the Challenger into the ocean. If the USN had
realized what happens to ballast blow valves (as they were designed before
1963) at depth (they froze solid) the Thresher might not have sunk.

What I am concerned about is limiting the delta between the incoming very
cold water and the much warmer tank interior. There are several ways to go
about that.

I've already taken one step, which is to reduce the incoming pressure to the
whole house. That slows down the amount of water that can enter the water
heater and reduces the potential thermal stress.

I'm also going to turn the water heater's thermostat down just to lower the
over all temperature differential. The cooler the WH output, the lower the
delta between incoming and outgoing water.

A third action is to trim the hot water feed valve to the washing machine so
that it doesn't draw anywhere near the GPM of a wide open valve. It will
take longer to fill (will be measuring that as we do laundry) but it's not a
very big thing to wait an hour instead of 30 minutes for the laundry to be
done. It's not like I am outside in the bitter cold beating the clothes on
river rocks. (-:

A fourth action will be to avoid the HOT only wash cycle during bitter cold
months (we typically wash our LBL dog's blanket in hot water), thus further
slowing down the amount of cold water that's introduced into the tank
quickly and lowering the thermal "shock" to the heater.

If I wanted to spend money, I might look into a pre or post water heater
expansion tank or put aluminum fins on the pipe leading from the master
intake to the water heater. That's at least 25' feet of copper pipe that
could transfer some room heat into the incoming water, but I think that's
way overkill.

I think reducing the pressure and the temperature while taking care not to
draw enormous amounts of hot water will substantially reduce the thermal
differential and the risk of catastrophic failure from thermal stress. It
will be just my luck that it fails as a result of crud getting into the
lines from the recent water main break, but at least I will have tried. (-:

--
Bobby G.