We live in Canada and have a pool and spa both networked together. In the winter we quit heating the pool but keep water circulating in both. we do this to allow continued use of the spa all winter and maintain water quality. The problem is during the winter condensation builds up in the heater when it's not on. I know it's caused by the cold pool water running through the heater which sits in a heated cabana. The question is can anyone recommend a heater that can survive in such an evironment, the current heater needs replacement after five years. Heat exchanger just began to leak and balance of unit is so corroded it's not worth repairing.