My Hayward sand filter gage shows 30psi. I have rebuilt the filter and the pump/motor, but pressure remains the same. I opened the return line union and pressure drops to 10-12 psi, so flow seems to be constrained in the return line. Back flushed the 3 jets, but none were blocked. Removed the balls in the jet outlets and pressure dropped to 28psi. Dug up return line to inspect it. It is a 45 ft run of 1.5" PVC to the pool, then it is reduced to a 1" PVC pipe. The1" pipe has a 40ft run to the first of 3 jets, then another 25ft to the 2nd jet, and another 15 ft to the 3rd jet. The pipe essentially makes a 360 deg loop around the pool, with 1.5" along one side, and then 1" around the other 3 sides to feed all 3 jets. I think all this pipe is what is causing the back pressure.
I plan on shortening the initial 45 ft run of 1.5" to 20ft put a T in and run the 1.5" about 5 ft to jet#3 and drilling out the small jet#3 and installing a large diameter jet (how large can I go?). I would also put a T in near the Jet#3 to allow also attaching the current 1" return to be fed "backwards" over to jets #2 then to #1.
Then from the T to Jet#1 from the 1.5" return pipe, continue 1.5" another 15 ft and install another T to go over to the pool and drill a new hole in the pool for a new 4th jet that will be a large one also. Then extend the 1.5" 10 ft to the reducer and tie into the existing 1" pipe to feed the other 2 jets. Replumbing the other 2 jets would required tearing out the entire pool deck.
This would result in a ring around the pool that is 1/4th 1.5" pipe with two large jets off of it, and 3/4th of it 1" pipe with two small jets off of it. Hopefully that would reduce the back pressure. What are your thoughts?