Our hot water heater was working perfectly fine then we had a water main break down the street. We were without any water for a day, and when we finally got water it will not get hot HELP

Is it gas or electric and what is the model number? I cannot see how a water main break would have anything to do with your heater going out unless you ran it out of water, then you melted both elements. If electric, turn off power to unit and remove both access plates on side of heater. You will see an element in each recess screwed into tank; it has a hex head, so you should have no problem seeing what it is. Remove one wire and using an ohm meter put one lead on each terminal. You should read 15-30 ohms. Read each terminal from one terminal to the metal side of tank-it should read zero. If it reads open on the first or any reading of ohms on the second one replace the element. Do this for both elements. Next, check the t-stats. These are in a square box shape. Remove one wire and read between the two terminals which should read zero ohms. The top t-stat has a high limit which should also read zero. Anything that does not read like it should must be replaced; make sure to test to ground on all tests to see if there is a short to ground.