My water heater runs out of hot water really fast, it has two thermostats there both set the same its 40 g

Question

it is a 40 gallon water heater so this should be plenty, i had smaller before in nother hoime and it was enough, does this mean one tank is not working? why would i run out of hot water so fast? how can i tell if one tank is not working?

Answer 1

The bottom element is open in does 90 per cent of the work since cold water is fed into the bottom of the heater. Turn off power and remove the wires to the bottom heater take a ohm meter to check it, if open it must be replaced.Shut off water to heater  and releif the water pressure you need not drain unscrew old element and slap in the new one if you do this fast you spill a little water due to the vacuum on the tank.  

Answer 2

The bottom heat coil/thermostat is most like broken.