I'm a follower of "THE METHOD" here, and I love it. But something is going on with my pool which I just can't solve. I apologize for how long this will be. I'm including a lot of gory detail at the outset; I can guess what many of the follow up questions will be.
My setup: 11K gallon fiberglass in-ground; SWG; Sand filter; 1.5HP single speed pump timed to run 14 hours daily. Testing is with a Taylor kit (a K2000 starter to which I added the FAS-DPD and other reagents necessary to test CH and CYA). My pool generally balances comfortably at: pH 7.2 - 7.4; FC 4.0 - 5.0; TA 80 - 90; CYA 60 - 70; CH 200. These are an average of recommendations I find here and those specified in the owners manual of my SWG (AquaRite). I have an automatic cover, but it's almost always open because I like to see the pool and I believe sunlight is good for the water.
-- Note: all chlorine additions below are 12.5% bleach; CYA was 40 ppm four days before this all started. I get 10 - 11 ppm FC increase per added gallon. --
Day 1: Early in the a.m the pool didn't look quite right. Test results: pH 7.2; FC 0.5; CC 0.0; TA 80. Something is wrong. Where is my FC? I put the SWG into 'super chlorinate' mode until I could buy liquid. Midday: FC 1.5; CC 0.0; and the pool was mostly cloudy. By 5:30 pm the pool was 95% cloudy and green with pH 7.2; FC 1.0, CC 0.5; TA 80 and CYA 60. I turned the SWG off and added 2.5 gallons of 12.5% liquid chlorine (targeting 25 ppm) to begin the shock (now it's SLAM?) process. Added another gallon before bed.
Day 2: Morning FC 15.5, CC 1.0 -- Bedtime FC 22.5, CC 1.0. 4 gal bleach added over 4 doses, one dose after the bedtime test. Pool was cloudy, but already significantly improved.
Day 3: Morning FC 27.5, CC 1.0 (approx 5.0 overnight loss) -- Bedtime FC 28.0, CC 0.5; 2 gal bleach added in 3 doses, none after last test. Clarity still improving.
Day 4: Morning FC 26.0, CC 1.0 (2.0 overnight loss) -- bedtime FC 34.0, CC 0.5; 3.5 gal bleach added in 4 doses. Clarity significantly improved - nearly clear.
Day 5: Morning FC 30.5, CC 0.0 (3.5 overnight loss) -- bedtime FC 29.5, CC 0.5; 2.5 gal bleach added in 4 doses. Pool is *almost* back to normal-looking.
Day 6: Morning FC 25.0, CC 0.0 (4.5 overnight loss) -- bedtime FC 28.5, CC 1.0; *5.5* gal bleach added in 5 doses, with 5th dose (1.5 gal) after final FC test. I am getting frustrated. Pool looks almost normal. Where is this chlorine going?
Day 7: Morning FC 35.0, CC 0.5 (9.0 ppm overnight loss???), bedtime FC 31.0, CC 1.0; 3 gal bleach added in 3 doses. Pool looks clear & inviting.
Day 8: Morning FC 25.5, CC 0.5 (5.5 overnight loss), bedtime FC 27.0, CC 0.5; *6* gal bleach added in 4 doses.
** Complete test results in early evening - pH n/a, TA *150* (???), CH 320, CYA 45ish **
Day 9: Morning FC 28.5, CC 1.0 (9.5 overnight loss), bedtime FC 31.5, CC 0.5; *6* gal bleach added in 5 doses, 1 gal of which was added after the bedtime FC test. It looks nearly perfect. I hate this pool. My wife is making noises about taking a sample to the pool store for testing.
Day 10 (today): Morning FC 24.5, cc 0.0 (~ 15.0 ppm overnight loss???). 1 gal bleach added so far, and as expected, FC was 37.0 , CC 0.5 approximately 40 minutes and one thorough brushing later.
- Monthly CYA test was 40 ppm four days prior to the start of this mess. At that point I added 3 lbs dry CYA via a sock in the skimmer targeting 70 ppm; pH was 7.4 at that point. At no point after that did I see it drop below 7.2.
- Pump has been running 24/7 the entire time
- Pool is completely brushed, bottom included, at least once daily, but usually twice. Until Day 4 or 5 water clarity decreased slightly after brushing. After that, brushing did not noticeably impact clarity.
- Vacuumed by hand on Day 5. There was some tree debris on the bottom, but really nothing much.
- Vacuumed by hand on Day 9. No debris on the bottom to speak of, but I felt like I should go through the exercise.
- Backwashed the filter twice over the above period, though I never hit the 20% pressure increase threshold. Filtration is a 200# sand filter with a bit of DE added.
- FAS-DPD reagent comes from a 16 oz bottle purchased late in the 2011 season, and which is stored in the basement when not constantly refilling the dropper bottle. The DPD powder comes from a 4 oz bottle purchased at the same time, and stored in the same conditions.
- As the pool clarity improves my chlorine consumption only appears to increase. I undertand the need for patience but I've averaged a 41 ppm FC consumption *per day* over 9 days, for half of which the pool looked completely clear.
- Did my TA suddenly spike because of all this bleach? I wasn't aware that could have an effect. I don't want to add acid because I really have no idea what my pH is (While at work the afternoon of Day 8 the FC slipped down to 16.5. I measured the pH at 7.5 knowing it would skew high due to the FC level). I should ignore the TA until my chlorine holds and I can accurately measure pH, yes?
- And finally, what happened that triggered this episode? At first I assumed my SWG cell had gone bad (this is its 5th season of service). I'm pretty good about maintaining the cell, with monthly inspections and periodic acid-washes. I've never noted any scale on it. However, the control unit never gave any indication of a misbehaving cell. The voltage and amperage while generating didn't change (that I noticed). So now I'm wondering if something got established in my pool and my SWG suddenly just couldn't keep up?
- I added 3 lbs of dry stabilizer to my skimmer in a sock, which I acknowledge was a lot. It took a couple of days to fully dissolve. Did this alter the pH enough at some point that I screwed up the balance? Even though I never measured a pH below 7.2?
I know what I need to do, and that's keep dumping in the bleach. But I've averaged a 41 ppm daily consumption rate when I'm accustomed to seeing 5. Where is all this *&^%$ bleach going?
Any advice & commentary appreciated.