Do you have a wiring schematic for a Rheemglas model 81V66DB ser # RH0500408476?

it does have 2 elements they are located under the 2 panels on the heater you will find them under the covers on the front they will be connected to the thermostats follow the wiring. besure to turn off the power before working on it and use a tester to double check

1) Copy following link for troubleshoot and replacement:
http://waterheatertimer.org/How-to-replace-TP-valve.html

2) Add comment Mar 2013 and say what you discover

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test the thermostat and the heating elements --also there are resets that can pop push and make sure they have reset

Make sure it's off (hydro) and open drain at cold line going in bottom wherever you find a drain (usually close to it) going down through floor and outside under trailer. Follow cold line back until you see a line "T" and one line going down under trailer, and open it up underneath. Then open pressure relief valve at top of tank to allow for faster draining .

Open following link to troubleshoot cause and solutions for leaking water heater:
http://waterheatertimer.org/Leaking-water-heater.html

Rusted water heater must be replaced.
http://waterheatertimer.org/How-to-install-gas-water-heater.html

For money-saving water heater information:
http://waterheatertimer.org/Replace-anode-rod.html
http://waterheatertimer.org/9-ways-to-save-with-water-heater.html

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One of the elements may be bad. With the power off check each one with an ohm meter. Should show continuity.

The tube the cold water come in through goes to the bottom of the tank. If it has come loose and the cold water stays on the top you wouldn't have much hot water.

Hello, The cold water dip tube is busted.How old is the unit?A plumber can make a new one but might not be cost effective.

You can repale it, but yes the tank will drain


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yes you will increase life if you flush sediment yearly