Hello, first time poster, long time pool addict...
My wife and I purchased a house two weeks ago that has a 26' above ground pool. Previous owner bought the pool used, had it installed professionally with a new liner. The day we closed (5/26), we pulled off the cover, filled with water to the skimmer, and fired up the pump. Good circulation, everything worked, a few equipment drips here and there but overall I was pretty satisfied. The water was green, with visibility about a foot below the surface. Having owned a pool before, I took the tact of adding some liquid shock (2 gallons), adjusting the PH, and seeing what would happen. As the week progressed, the algae got worse. I added two additional gallons of shock, and 6 1lb packs of granular shock, during the first week. The two way test kit showed plenty of chlorine, ph acceptable at the end of the week. This past weekend I opened the sand filter up and found the stand pipe cracked. We deemed the existing pump (1.5 HP, bearings were very noisy), housing (cover cracked) and broken filter not worth fixing; so I purchased and installed a new 1HP 18" Hayward Pro filter/pump combo. I used three 25lb bags of ZeoSand, backwashed, and set it on filter. Initial PSI was at 16. Aimed the eyeball down and to the right, creating a lazy counter clockwise spin to the surface. Beginning Monday, using the WalMart 10% pool bleach, I added: 3 gallons Monday, 2 gallons Tuesday, and 2 gallons Wednesday. On Monday, I ordered a TF-100, which was delivered yesterday. Last night I did two tests, TC and CYA. TC was at 35, and CYA was between 90-100. I tested again this AM and came up with the same results.
Based on the TC/CYA chart, I need FC around 40 to be at shock levels. This verifies my theory that when I began blindly adding chemicals the CYA was very high to start, and the shock added to it, creating the problem I have now. I simply wasn't adding enough liquid chlorine to bring it up to shock level, and that is why the algae is now worse than when I started.
I am contemplating draining the pool and refilling. A local pool water delivery company can deliver 6K gallons for $275. It is public drinking water from a local municipality. I have a well with high iron, and between battling an iron problem in the pool and killing my well, it seems that $275 may be a bargain. This should bring my CYA down to a more manageable 50-60, and rid the pool of some seriously green water. Based on the Pentair pool volume calculator, a 26' round pool at 1.5' depth is just at 6K gallons.
So, my plan is: drain 1.5' of water (leaving 2.5' in the pool), fill with new water, circulate for two hours, and take all new baseline measurements using my TF-100 test kit, and go from there. The only downside I can see to this is wrinkling the liner, however, I've read that leaving 2.5' in the pool should be ok.
Am I on the right track? Thanks in advance for any input