Originally Posted by bubbles
Cannot visualize how WH affects the toilet input. If you have winterizing valves on the back of your WH are you sure they are turned all the way in the right directions?
When the water in the water heater gets hot, it expands.
When it expands, it also increases the pressure throughout the entire plumbing system.
When the pressure in the entire system increases, it can cause a leak at the weakest point, which in this case is the toilet connection.
This scenario may turn out to not be the OP's problem... but it could be.