I installed my water heater 10 gauge wiring to the breaker box 30 am breaker. The breaker only has a white common, black hot and ground so I don't have power from the second red hot line. The house is 70 years old. Can I install the red line to a second hot breaker with a white common and another ground? If not then will I have to have another sub panel installed because there isn't any more room in the old breaker box.

I installed my water heater 10 gauge wiring to the breaker box 30 am breaker. The breaker only has a white common, black hot and ground.The second breaker box has all 30 am breakers with only red hot lines. The house is 70 years old. Can I install the red line from the second breaker box and the black line and ground from the 1st breaker box to the water heater? If not then will I have to have another sub panel installed because there isn't any more room in the old breaker box.

On the main panel the is a 100 amp double breaker and two 60 amp double breakers. The previous owner ran line off one of the 60 am double breakers for the washer and dryer. I guess I will have to run 10 gauge line to a new breaker box off of the main panel and then in to the hot water heater. Thank you for your advice.