Hi. Noob here. 21,000 gal, in ground, from 1970's. Pentair 36 DE with 2" slide valve. Dead Hayward type PS Replacement Series .75hp pump. 1.5" piping at pump and filter (except 2"@ slide valve) reducing down to 1.25" outlet & return lines at slab. All PVC, no flex tubing. No heater, chlorinatior now but want a few solar panels some day. Will a WaterWays PD140 work well here? How about a flow meter? What size meter? In So. California. DYI guy.