Great idea about the salty ice water. I went out to try that this afternoon, but before I did that, I wanted to see how the valves operated while not in freeze protection mode. When I selected spa on the controller, both valves moved simultaneously as expected. I did notice a very slight drip out of one of the valves while the valve was transitioning, but it stopped as soon as the valve got in position. More concerning was the pump. When it turned back on, the water level in the pump skimmer basket was below the intake pipe level, and it stayed below the intake level for the 10 minutes I let the spa run. The water level in the spa stayed at the top for the entire 10 minutes. I thought that maybe the sand filter was in need of a backflush, so I returned the valves to pool mode. The sand filter pressure gauge was at its normal level, but I went ahead and backflushed for a couple of minutes anyway. The backflushed water looked pretty clean. When I restarted the pool pump, the pressure gauge was at the same level as pre-backwash. Then I put the pump in spa mode. Unlike the first time, the skimmer basket water level was at the top when the pump started, but after about 5 minutes, the water level was once again below the intake pipe level. That cannot be good. The other thing I noticed is that the sand filter pressure gauge was only about 3 psi higher than when in pool mode. Usually it's at least 6 psi higher. Where should I go from here?