I have a Hayward system with a pool that has a spa with spillover. When I turned it to spa mode & filter from my Aqua Pod remote control all of the water drained out of the spa.
I was able to get water from hose to stay in the hot tub when I changed it to pool mode with filter off. This happended one time a couple months ago and the pool guy said my actuator (far right in pic) was broken and he replaced it. He said it was a fluke that my spa drained. The pool is only 2 years old...
These arrows in the picture are which way the actuator handle is pointing.
spa mode filter on.jpg
pic above in spa mode with filter on
text boxes on pipes from left to right: main drain, deep skimmer, shallow skimmer, pool return, waterfall, bubbler fountain
equipment in pool mode.jpg
pic above in pool mode with filter off. both actuator handles are are pointing inward
The last pic is me trying to fill spa with a hose. Water will only stay in spa if I change to pool mode with filter off. I think last time this happened, we did pool mode with filter on and the spa filled from pool water (no hose needed)