1) Test results TF-100 drop based test kit include:
Combined chlorine, using an FAS-DPD test: 5 ppm
(Tap Water TA: ~ 130)
Salt" : n/a , no SWG
2) The gallonage of your pool OR it's shape (rectangle + Grecian Ends) ~30' x ~ 18' x ~5' or est ~20,000 gallons
3) The finishlaster
The form of chlorine: was trichlor tabs with occasional 12% poolstore NaOCl, now only Clorox 6% NaOCl.
4) Whether you use any metal or '"mineral" sanitizers: none
5) What the water looks like: clear, (plenty of bleach eventually cleared the green algae)
6) The kind of filter: cartridge
7) Location: SF Peninsula, California
Had not understood TriChlor contribution to CYA build-up. Had CYA ~ 200 assuming CA viewtube is approximately
a log scale. Drained ~ 1/4 pool water to reduce CYA to ~ 100 as listed above. Taylor K-1000 TC goes off-scale
with redish precipitate; diluted to 50% tap water 50% pool water and TC is 5ppm or more.
Algae now under control. Thinking I should reduce CYA, but nature will provide 100% fresh rainwater in
~ 2 months to dilute/replace pumped out pool water tainted excessive CYA. Too much FC? Still see whisps of algae
when I brush the pool down, and plenty on/in the cartridge at backwashing.