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. I
completely drained the water heater, vacuumed out the sediment, then
refilled. I set the thermostat to 120. People were still complaining that
the water wasn't hot enough. So I raised the temp to 130. Less complaints
now but there are times (one person says they have good hot water in the
morning, but none in the evening) when people say they run out of hot water.
I called the water heater company for some tips and was told that if some of
the units have a single handled faucet in their sinks, the hot and cold
water might be mixing together causing the problem. I know that several of
the units do have these single handled faucets and I should have taken
detailed notes when I talked to the tech as he explained how to troubleshoot
this particular problem. So what is the step by step procedure to pinpoint
this type of problem?
Thanks for your reply.
Is the recirculator pump new, on a timer, or thermostat. Have you
measured the tenants water temp, many complain, just to be sure they
are getting their rents worth. You only need 106-107 out of the shower
head to take a hot water shower at the furthest point. Im sure your gas
bill is high, your tennants don`t care, you pay for it. I would check
the temp yourself first after you cut it back to 117 or less. You need a
timer and thermostat on circulators or you are just running a heating
system. I hope all your pipes are insulated. If your faucets were
leaking I would worry. You need to be the one to determine what temp is
needed, not your tennnts, its your profit.
The recirculator pump was purchased and installed new when the heater was
installed. We had the old pump connected to a timer but it took way too long
for hot water to get up to temperature during the off hours. So the timer
was disabled and it was on continuously. Perhaps with the new installation
of equipment, that is not true anymore.
The pipes around the water heater are wrapped in foam. I don't remember
seeing any similar insulation on exposed piping in the building. i.e. shut
off valves in closets adjacent to the tub/shower.
It looks like I'll have to test each sink and shower for leaks and bring my
thermometer with me.
Thanks for your reply.
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.
Looks like a pretty hefty pump.
Monitor (by hand) the temp of the water going *into*
the pump; IOW in the vertical pipe feeding the pump.
Normally, that should be at least luke-warm .
See what happens when many tenants are using hot water.
If the temp of the Hot supply out of the top of the
heater is still Hot but the Return pipe gets Cold,
suspect reverse flow.
Oooooooooooooo One thing we hadn't considered
was a bad dip tube. A broken dip tube will give
nice hot water **except** when many tenants are
demanding water. Then, although the heater is
full of hot water, the incoming Cold water
will simply "short circuit" and go out the Hot pipe,
diluting the temp.
Regarding the dip tube, when I was cleaning out the heater, there was a tube
right next to the clean out hole that was in tact though it did have some
lime build up on it. It reached to almost the bottom of the tank. I figured
that was the dip tube and it wasn't broken.
Just to recap from my original post, I had set the thermostat to 130
degrees. The temperature of the return pipe and the hot supply pipe were
about the same. I measured the temperature of the water at the utility sink
located near the water heater. It was a lukewarm 107 degrees. I called the
water heater company yesterday to report my findings. The tech said to check
for cold mixing with hot by turning off the cold water to the heater. Then,
turn on the hot faucet and there should be no water coming out. I tried that
and there was no water coming out of the hot faucet. He also told me to
check the water temperature at the relief valve. It was 116 degrees. I
called back with my findings this morning and spoke with a different tech.
His conclusion? The thermostat must be out of calibration due to lime build
up. Either replace the thermostat or turn up the thermostat until the water
temperature is at the desired temperature. I gave the thermostat about
another 8 degree boost to 138 degrees and finally the gas came on. I'll go
back later and see what the actual water temperature is.
Thanks for your reply.
Do any of the shower heads have a secondary shutoff on the shower head? If
so and the person uses the shower head shutoff and leaves the hot/cold
handles turned on then, hot and cold can mix in the pipes all day long.
The same thing can happen with portable dishwashers or clothes washers
attached to the kitchen sink faucet.
Also laundry, utility, or janitor floor/mop sinks and such can do this if
you leave a hose with hand sprayer attached and with the hot and cold valves
I would think a defective single handle faucet could also mix hot/cold but I
would think they would also be leaking/dripping. Check for defective clothes
washer valves etc.
Any complaints about warm water in the cold taps or toilets?
Also 100 gallon does not seem like much for 7 units. I don't know maybe it
is if the heater has a good recovery rating? Does the same heater supply
the laundry? Maybe check with other landlords with similar sized buildings
and see what they have.
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