I need help in keeping my PH up high. I'm trying to reach 8.0 ph in order to flock. The pool in a 25,000 gal in-ground pool. The pool has been closed for 2 years and we descided to open this year. The pool was a swamp and was loaded with leaves. We have pretty much cleared 95% of the leaves. I shocked the pool many times keeping the chlorine at least 10-15ppm over 2 days. My sand filter has some air in the system and we have not been running that as much. The water looks grey-blue with fine particles all through. We tried filtering but found we loose prime after the filter's pressure get's a little high. We then backwash,rinse, & back to filter. We have been doing this for 2 days with little results. So I'm here needing some advice on why my PH will not stay high. My last P.h. reading was 7.2 so I added 1 1/2 boxes of 20 mule borax to get it to 8.0 in order to flock. After checking it the P.H. did not rise as much. I'm using a 2 year old test kit. 5 drops of red solution. Getting a new test kit soon.

Alkalinity: 110
P.H. 7.2 <----no change after 1 1/2 boxes of Borax.
F.C. : 6.0
C.C. : ?
CYA: 20-25

Poor filtration at this point which I know is half the battle. The sand is only 2 years old with 1 of those years being used. I also used a sand filter cleaner before starting up. Still need to find the air leak. The filter is working somewhat if only at 60% efficiency because it is capturing some particles causing pressure build up.