I have a pool spa combo when in standard pool fiter mode flows from the spa in to the pool. My problem is when I am running my spa the water level drops quite significantly. It have gotten down to the point of the jets being exposed. So I have to keep putting it into spa fill mode to get the water level up. Any ideas as to what might be happening? I do not think it is a leak since when I put it back into regular filter mode the water level is the same. Also any suggestions on remedies please.