I have a 40 gallon electric hot water heater in my apartment. The hot water runs out after a 10 minute shower, by the end of the shower I can turn the cold side all the way off and the hot all the way on and it is freezing cold. This is a new hot water heater (supposedly) because they replaced both elements and thermostats in the last one and that did not solve the problem. So, how long should 40 gallons of hot water last? And if the problem isn't in the elements or thermostats then what else could it be? The maintenance crew seems to only think it can be the elements or thermostats. I did turn up the temperature to 150 and that did not help.

Citichick - DO yopu have a ( VOLT-OHM
METER? ) If you do ,lets do a little checking
AND we may find the cause You may have a bad THERMOSTAT or A BAD HEATING ELEMENT!! Probably the element. :: Ok take the cover off the TOP THERMOSTAT AND heating element is under it (NOTE - POWER IS ON, BE EXTREMELY CAREFUL ) SET you meter to 250 volts scale , take and touch a probe from the meter to each screw on the top of the thermostat ,where the main wires come in from the panel box ( ELECTRICAL ) You should get a reading of 220 Volts, if you do then you are OK ,from the electrical panel box . ( #1 )- Lets check the top thermostat first , Make sure the red button ( RESET ) is pushed all the way in and not tripped , If OK ,Turn off the power at the panel to do more, Power is off ( with meter set on RX- scale ,Touch meter probes to the screws with numbers 1 & 2 0n the thermostat, Watch the meter readings, Now do the same to screws, 3 & 4- If the needle did not move towards the zero on both tests then the thermostat is bad and needs to be replaced, Put the probes to each one of the screws numbered [3 & 4 }on upper thermostat, If the water is cold in the tank then the needle should remain on the figure 8 laying down, if the water is hot the needle may swing towards the zero, if it does turn the tempture screw up to a higher temp.reading ( LISTEN FOR A CLICK AS YOU TURN THE SCREW TO A HIGHER TEMP> When it clicks the meter needle swing back to the 8 LAYING DOWN, If not then replace the thermostat. Put the tempture back to normal setting With probes touch both screws on the heating element If you get a meter reading then it means the element is OK ,BUT Believe it or not but the meter just lied to you if The needle had moved, (WHY) BECAUSE IF THE ELEMENT JUST HAS A TINY HOLE IN IT AND WATER GOT INSIDE THE ELEMENT THE COUNTIUNTY WAS COMPLETED AND SHOWED GOOD < EVEN IF IT WAS FULL BLOWN OUT , { THIS IS MORE THEN Likely WHERE THEY MESSED UP , To really get the true reading a heating element you have to double check it , to do thisd PUT ONE PROBE ON ONE OF THE SCREWS ON THE ELEMENT ANT PUT THE OTHER PROBE ON THE METAL TANK< IF TANK IS NOT METAL TOUCH THE BRACKET THAT HOLDS THE THERMOSTAT< IF YOU GET A READING THEN REPLACE THE HEATING ELEMENT < WHEN YOU GET IT OUT CHECK AND YOU WILL SEE THE ELEMENT IS BLOWN AND FULL OF WATER ( SO REPLACE ELEMENT:: DO the same to the bottom thermostat and heating element:: If what I have given you to check out does not prove out , come back on to this thread and post it and will get back to you on what to do next , Good luck and have a better day tomorrow, and GOD BLESS ::F.B.E.
I do think this is where you will find the trouble at , If you don't do this ,watch and see if they do it this way , Good day ::: F.B.E.