Well, I would think that when you set your t-stat so the tub is the right temp. then you will be fine to keep the probe on the flexwatt. Think about it, if the flexwatt stays the same temp. which works, then it shouldnt effect the temp when you put the tub back in. Now of course the tub temp is gonna be cooler/hotter depending on your room temp, but eventually the tub will adjust back to the same temperature!