All was fine as of yesterday - I backwashed and rinsed, then set back to filter mode and left circulation on overnight in order to heat the pool water up for use today. This morning I noticed an unusual sound from the skimmer basket - and when I took the cover off from the coping area, it looked like the water was being pulled into the skimmer area in a steady stream as if it was being suctioned through like a vacuum. The main filter and lines in our pool house were also making unusual sounds, as if water was draining (the backwash line was shut). I shut off the filter. The water level in the pool was on the lower side from the backwash, however not the lowest it's been, so I topped it up, ensured all filter baskets were clean, checked that all valves were set as they should and turned the filter back on.
2 of the 3 return jets are not flowing normally - water is passing through but it's intermittent, humming and causing unusual bubbling at the surface near one of the return jets.
Sorry if I am weak on the terminology here and please let me know if I can provide more info - any ideas on what could be going on? Or should I just make a service call?
Thanks as always.