Larry, (Dayton, OH)
You’ll have to gain access to the existing valve anyway. And since you’re going to that extent, simply install the electric valve and forget about cables. Just push a button! Just remove the existing valve (sandwiched between two adapters at the tank outlet) and install the new electric valve. Make sure the valve body is oriented vertically; the more vertical, the better, even if it’s only slightly upwards. In fact, EVERY termination valve should be mounted in this manner to avoid waste and crud from entering the body cavity of the valve. This will eliminate the possibility of the residue drying out and putting a bind on the sliding gate portion. This is typically why termination valves fail in the first place. RV manufacturers simply should not mount termination valves horizontally or angled downwards, yet it is a very common occurrence.