Originally Posted by Stratos201
... I will check the element and I might just replace the breaker to make sure that isn't the problem.
It's difficult to diagnosis over the internet as the information trickles out.
Do you know if the A/C was starting when the breaker tripped? The system design would expect to have the A/C operating with the electric water heat option enabled. Was there anything else running? Hot air hair blower? Electric space heater? Do you have a 120 volt compressor type refrigerator?
I wasn't suggesting that the heater element is the problem. Every breaker trip is not necessarily related to general overload. I just wanted to point out a grounded element as a possibility.
With all other heavy loads off, if a beaker still trips every time the electric water heater is enabled, then check the element and related wiring. Otherwise it may well have been a general overload situation.
It may be worth inspecting the wiring/tightening all the connector screws in your panel. Low voltage from poor connections can contribute to general overload.