I have a new pool with a raised spa with an overflow. Now that it is winter I want to run without the overflow on. The problem is that when the valve turns from spa to pool mode water drains from the spa drain to the pool (clearly because the relative height of the spa drain). Without the overflow on each time the valve goes from spa to pool more water is drained until the spa is empty. This means I cannot have the system in freeze protect without the overflow on. Surely there is a fix for this? Thanks for any help.