Had a pool since 1981 and am really stumped.
Started having some air in pump issues with Pentair variable speed pump. Unit was located about 5 feet from skimmer and about 18" above bottom of skimmer.
Thought I would address along with a pump relocation....Yea now I know that was a bad idea. Moved equipment 25 feet away to get out of sight and mind. When I started back up had a larger bubble in pump basket and would only fill salt cell up about 1/4 of the way...sometimes producing low salt alarm.
When I relocated I used 20' section of pipe so only added one extra joint on each end. Did alls the usual stuff..new oring for basket, lubricated all orings and drain plugs and everything never got better. Pump was cavitating and only way I could stop was to close back the return valve till cavitation stopped. Checked for debris in the impeller but it was clean. Skimmer vbasket clean, flapper working and water level good.
Pump was 5 years old so figured it needed new seal and stuff. Took pump into shop and explained my symptoms I wanted a spare pump so bought a supermax 1 hp and thought I would just install and then fix varliable speed pump and reinstall when I got around to fixing it.
Would you believe same problem!. I was ticked to say the least so I wanted to eliminate anything under the deck. I installed 35' of 1.5" PVC to the suction of the new pump and ran it to the pool and ran it about a foot under the water. So this had to work, right? NO!! Now still about half of pump basket window is still a bubble and salt cell is only about 1/2 full. Hooked back up to underground piping and got the same half window bubble and 1/2 full salt cell. Used shaving cream on every visible joint and fitting with now air leaks.
Simple system two returns, suction from skimmer bottom only all 1.5" pvc.
Pump curve says I should be able to get full suction at 40'. I am at 33'. BIG question. Should a 1 HP pump pull through 1.5" pipe for 33' and push through a 200# sand filter? Is there anyway a super cleaning of the filter help this or am I too far away?
Also, new gauge is high about 25PSI