1. Inside your water heater is a rod-like device called an anode. This exists in the water heater to prevent rust, and is also the best way to determine rust levels in the heater. In order to check this piece, you must first make sure that you turn off the heater.
2. Remove the anode from your heater and inspect it. When the rod itself looks like it has been damaged, or if it has been worn away by time and use, then it means that rust levels in your heater are severe. If the anode looks as it should, then you are in good shape and can wait a few months before checking the rod for deterioration again.
When you find that the rust in your hot water heater is too bad to be functional, it is important to have the device replaced. Visit this website for more information on water heating replacement in Vista.