"Speedy Jim" wrote in message
. com...
David Farber wrote:
We have a two year old, 100 gallon, 199,900 BTU natural gas, American
Standard water heater supplying hot water to a 7 unit apartment
building.
Installed with the water heater is a recirculating pump. Each unit has
one
bathroom/tub/shower. Recently, the hot water supply has been
intermittent.

SNIP

I agree with AmStd, this doesn't sound like a heater problem.

Besides the single handle faucet cause, washing machine
sol valves can "cross-connect".

Another possible is the recirc system.
If the return pipe to the heater doesn't have a working check-valve,
cold water from the heater bottom can flow *backward*
up the return pipe to the Hot faucets.
Even though there is a pump, the recirc system can be overpowered
by drawing Hot water and will pull from the return if the
check doesn't seal.

Jim

I will have a look at the check-valve situation. A fault there would
definitely cause strange temperature problems to occur.

Thanks for your reply.

--
David Farber
L.A., CA