What is the top thermostat supposed to be set at

Copy following link for tank-type electric water heater troubleshoot:
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html#skyrocket

Press reset button located on upper thermostat.
Test elements for short to ground against steel tank.
Clean sediment out of tank. Check for water leak running hot water out of tank.
Replace both thermostats.
http://waterheatertimer.org/How-to-replace-thermostat-on-electric-water-heater.html

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

120V on each screw terminal of the top or upper thermostat. Rheem use and care manual.

The most likely problem is that the thermostats are set too high. Remove the thermostat cover plates and look to see where the thermostats are set. The range should be between 120F and 135F. Liquids expand with heat so the higher the temp, the high the pressure. Decrease the setting on the thermostat until the leak stops.

The other likely cause is a head of air trapped in the top of the tank. After drawing hot water, it wiill be displaced by the incoming cold makeup water. This will compress any air in the top of the tank. As the water heats, the air will heat and pressure will build - possibly causing the leak. You can purge the tank of air by opening the pressure relief valve until water comes out (which I assume that you have already tried).

http://www.rheem.com/product.aspx?id=09DF2BDD-5E11-4D32-B574-84ACFB8A4619
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82V80-2 Energy factor is .86 according to water heater industry self-regulated standards.

Rheem pdf says these water heaters are wired for non-simultaneous operation.
Except special order water heaters.
Non-simultaneous operation uses single 240V circuit as described below.
If your water heater is wired for simultaneous operation, and each element is on a separate circuit, that makes your water heater special order. I would guess the reason is for higher first-hour delivery, which implies rapid heating and would likely affect energy factor.
You might want to get serial number off model and call Rheem for specs on that special order.

Your water heater energy factor may be the same because 'energy efficiency is based on the amount of hot water produced per unit of fuel consumed over a typical day.' This means an aircraft carrier can be considered highly efficient despite overall cost. And naturally the guys making the aircraft carrier are also doing the rating.
http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=13000

Non simultaneous operation means the upper thermostat controls heating functions.
240V goes to upper thermostat first.
When water inside tank is cold, thermostat reads temperature through tank wall.
Upper thermostat turns on upper element until top 2/3 of tank reaches thermostat set point.
Once set point is reached, upper thermostat turns off upper element and sends power to lower thermostat and lower element.
Lower thermostat reads temperature through tank wall, and turns on lower element until bottom 1/3 of tank reaches thermostat set point.
As water cools inside tank, lower thermostat is first to respond since hot water rises.
Lower thermostat turns on lower element until tank again reaches set point.
When hot water faucet is turned on, hot water exits top of tank.
At same time, cold water enters bottom of tank through the dip tube.
The heating cycle repeats.
At all times, the electricity flows through upper thermostat. And upper thermostat is powered by one 240V circuit.

With simultaneous operation, the upper and lower thermostats work in same manner.
Except thermostats are wired separately.
Lower thermostat does not wait for upper part of tank to be heated first.
Lower thermostat turns on whenever lower part of tank cools.
The advantage is more hot water available rapidly when demand is high. This is called first hour recovery.

One method for reducing electric consumption is to set lower thermostat so it only turns on during certain times of day. For example Whirlpool Energy Smart operates in this manner and shaves a few bucks off the bill each month. This says that simultaneous operation is not an energy saver, unless that circuit controlling lower thermostat is set on a timer.

Expansion tank is supposed to stop over-expansion due to pressure.
The check valve will stop over-expansion from pushing pressure back into the supply line.
The real question is what is causing the pressure.
If your TP valve is bad that could cause problem.
If the thermostat is set very high, and there is frequent short-term use of hot water, that can cause heat to build up inside tank.
Solution:
Lift TP valve and let out pressure to see if there is something lodged in the valve.
Be careful of the scalding water.
Let the TP lever down slowly.
Next step would be replace TP valve.
Turn down thermostat to 120, or set to 130-5 if objective is to kill most bacteria.
Last. You might check that your expansion tank is correct for water heater.

There are two access panels on the heater, remove screws to access it. They cover the upper thermostat and element and the bottom covers the bottom thermostat and element.
The top thermostat is the main one that has a reset button along with a dial to turn up the heat for the top element. A white plastic knob that you can use a flat head screw driver to turn to adjust.
Also you have one on the bottom to turn to adjust the heat on the bottom.

This is how you adjust thermostat's to increase to a hotter setting.

First things first, you are not supposed to have power to both elements at the same time. The top element comes on and heats the top of the tank, then the top goes off and the bottom comes on. Now, check power on the top element, put your meter probes on both screws on the element, you must have 220 to 240 volts between these two screws. If the voltage is good then you have a bad element, if the voltage is not there, then you need to check the voltage at the top 2 screws on the upper thermostat, if it is okay there, maybe the hi limit has tripped, push the reset button on the top thermostat, if it is tripped it will click and start heating right away. If the hi limit is not tripped then you will need to replace the upper thermostat.

I have the smae problem but my element on top works fine it is the element on the bottem that does not go on so what is it that i have to change the element or the thermostat. on the bottom or the one on top. I have voltage on the top but none on the bottom element and are they suppose to go on the same time.

that is the flow to the pilot lite and no it is not supposed to be readjusted, if anything you should get the numbers off the gas valve and replace it, or depending on the age of the water heater get a new one,

Not exactly, the heated water in the tank it self is roughly the desired temperature of the thermostat, there is a variable of 5 to 15+ degrees depending on its calibration. there are other considerations i.e. water heater tank insulation - hot water pipes being exposed to cooler temperatures thus cooling the water in the pipe - the farther distance that the water travels from the heat source, the cooler the water will be at the spigot.