The Hot Water Tank is Owned not Rented, therefore it's not a simple phone call to Hydro to come fix. Is there not 2 separate elements in the tank? Can they be checked to see if one is defective? We draw from a Well , the water is Hard and Rusty if not treated.. We have a UV light and Water Softener as well that does an admirable job at clearing the hardness & rust staining...

Several things could cause this problem.
1- A faulty element **or**
2- a broken dip tube, (see image).
Also, if your water has rust and minerals in it you should flush,(not drain) your heater on a monthly basis, CAUTION! The elements work on 220 volts which can be lethal. Good luck, Tom