Hi, I'm Jim, sorry to sound so desperate on my first real post... but I'm really at wits end with this pool.
Sylvan, concrete (gunnite?) 40x20 with an 8x5 attached spa that has a spillway between the two. 3' deep at shallow end 8' deep at deep end. 2 skimmers, 2 floor drains in the deep end, 2 floor drains in the spa, one vacuum port, and 2 tiny pool returns. Pump is a Pentair Whisper Flo PN 011514 - Filter is a Pentair FNSP 48 - there's a heater but I haven't used it and have no idea what make or model is. There is also a Hayward cartridge filter on the vacuum line.
I usually have the skimmers set at full and the main bottom drain at about 30% and the spa drain shut off... I have it all returning to the spa. This setup has worked well for 2 years.
The pool was fine a week or so ago but overnight turned milky white. Checked the chlorine... none. Shocked the pool, filled the skimmer up with tabs, washed the filter out, added DE... DE blew back into the pool. So I got a new filter thing for inside the housing, the whole entire assembly. Installed it, added about 2 coffee cans of DE, none went back into the pool... everything is operating perfectly but the water is still milky. About a half hour later my wife noticed that no water was coming over the spillway. Opened the filter, clean as a whistle.... put it back together, turned it on, worked fine for about a half hour... then water stopped going over the spillway again.
So I started messing with the valves...and figured I had a bunch of blockages, took the valves apart ran a snake through them, used a hose cleanout bladder... nothing came out, no real issues with the bladder. So I ran the pump overnight with the vale set to recirculate. Ran fine, no flow issues whatsoever ... but pool is still milky (obviously... the filter wasn't involved). So again today I messed with the valves and I can get everything to work for about a half hour... then the flow stops. IF I backwash it twice it runs for another half hour. Doesn't matter if I backwash it for 5 minutes or just a quick on off with the power switch... all I get is a half hour of flow.
I have not added DE back to the filter - I ran it most of last year without DE and it operated fine. I also have a robot that I've been running around the clock just to help move the water a bit... but that's pretty much been useless.
What in the heck do I have going on here? Can anyone point me in the right direction? Would pictures help?
EDIT - The filter pressure gauge used to run about 20-22 PSI... now when I backwash it it drops to about 18... then slowly works its way back up to about 30-32. The higher the PSI the lower the flow over the spillway.