On 5 Mar 2007 06:03:39 -0800, "mdo" wrote:

I just bought a house, and the hot water tank was only 6 months old
when I moved in. We've only been in it a week, but it seems that if
two people have normal (5 - 10 min) showers in the morning, the hot
water runs out by the time the second person is half done. I know
noting about a hot water heater except how to change the temperature
setting, so am a little lost here. Does anyone have a comment or
suggestion about what may be going on, or what I can do before I have
to call a plumber? Thanks in advance.

Is this electric or gas??????? Or solar?

If you have two heating elements in the wh, the bottom element or
thermostat may be broken or defective. IIUC that is much more likely
than the top one. (actually I don't know what happens when only the
top element is defective, but I think the water doesn't get hot at
all.)

Turn off the circuit breaker, take off the cover, check with a
voltmeter set to 240Volts AC or higher any two contacts that you
intend to measure in any other way, and then IF THE VOLTAGE IS ZERO
measure the resistance between the two screws on the heating element.
It should be very low.

Try to figure out which two are the proper ones to measure across the
thermostat, and after measuring for voltage, and IF THE VOLTAGE IS
ZERO, measure the resistance there. It should be zero.

If the heater resistance is not low, or the water is not hot and
thermostat resistance is not zero), that part probably needs
replacing. The part is less than 20 dollars iirc.

If the water is hot enough, even if the circuit breaker has been
turned off, the resistance across the thermostat will be high or
infinite. But that is normal when the water is hot enough.