I shut off the main in order to change a shower cartridge, when I turned the main back on all I can get is warm water. Both valves to the heater are on, it is a rheem professional 612. The main shut off is a ball valve style.

Beside the shower do you have hot water?

Please tell us the Model and the brand of your shower valve, Thanks.

John

Sorry, it is not only the shower. \when I turned the water main back on, I do not have any hot water through my house, only luke warm

Sorry, it is not only the shower. \when I turned the water main back on, I do not have any hot water through my house, only luke warm

Drain some what from the drain spigot at the bottom of your heater, is it really hot or luke warm like the rest of the house?

It is luke warm like the rest of the house. Checked the element with a test light and it appears to be bad.

There are likely two elements , one top and one bottom. Not knowing how you tested the elemeent it may be bad or the thermostat may not be calling for heat. You should not be using just a test light for this. Electric water heater repair: how to test the heating elements or electrodes

Tested both elements. They were fine. Thanks for the link. Plumber just left and said it is probably the result of dip tube failure

Not likely a bad tube. With a bad tube you get hot water which would turn to warm and then cool. If both elements are good I'd check the stat setting

He said that both stats were good, not exactally sure how to check the setting, the water does start hot, then goes to warm and eventually cools down

Until this post you have been saying all along it was luke warm so this is news to me. This then could be a bad dip tube. "start hot, then goes to warm and eventually cools down"