Weird issue, pump basket water level drops after an hour or so (no air in filter when I bleed it), spa equalizes after pump off within an hour. Check valves all replaced, Pentair valves all rebuilt, checked piping with suds. Also, when I run solar I get bubbles all day, ramp up pump speed and bubbles get worse. Everything I can find says it’s a suction side leak...No, if it’s a suction leak you will see the pump lose water when it’s shut off. IE the whole system is no longer primed, the moment you introduce air the whoosh effect takes place.
FINALLY! Another set of eyes noticed that the pump wasn’t sitting “flat/level”. Leveled pump, lubed union o-ring and now everything is back to “normal”...If you’ve changed nothing then I guarantee there is a bad o ring, bad cover fitting or spider crack somewhere.
Also check the weir to be sure it’s free floating and not stuck in closed position.