Hello everyone! I've been reading this forum for a while now and have learned a lot of great information, though I'm having a problem that I cannot seem to find an exact answer to.
TL;DR: History
I have a rectangular in-ground pool about 3 years old, approximately 18,000 gallons. This was installed by the previous owner and this is the second season for me. It is chlorine, has a sand filter, retractable cover, chlorinator and UV filter. We keep the pool covered nearly all of the time, opening it when we swim and closing it afterwards. Last year the pool was maintained bi-weekly by the company that installed it, and they opened and closed it for the seasons each time. I had been doing the general chemical maintenance and checking last in between their visits and didn't really have any issues. This year they informed me that they just don't have the resources to do pool maintenance visits and to find someone else. Given my experience last year I figured I could handle it in the meantime while I found someone else.
This year when they opened the pool at the beginning of May after being covered since end of September it was pretty murky and teal colored. They added an algicide and a lot of shock and said to give it a few days and should be fine. It seemed to clear up after a few days though given the cooler spring the water just wasn't warm enough to swim so it got very little use in May. I did periodically test it with my test strips from the previous season but was getting somewhat erratic results so just figured they were no longer good and needed new ones.
During a particularly rainy week we were out of town for about 5 days and when I came back the pool was back to being murky and teal again. The PSI on the filter was 23 (should be max 20) and when I backwashed it, it had a noticeable smell. Afterwards the PSI was back down to normal. Over the course of a few steps, I added the recommended amount of HTC algicide, shock and clarifier and waited. After a several days it began to slowly clear up, however that's when the problem really started...
The problem (finally)...
In short, the pool does not and will not hold chlorine. Over the course of the past three weeks I have probably added 20+ gallons of liquid (10%) and 2 maybe 3 containers of granulated. Consistently after about 4-6 hours the free chlorine was down to below 1, sometimes looking like 0. The CC seems to remain proportional to the FC where when one is high the other is high and when low they both are.
I continued to pour 4 to 5 gallons per day seeing the same results. We brought in a new pool company and they reported on the first visit that the pH was also very low (below their lowest measurement on their strips). I had seen this as well but was very inconsistent across the different types/brands of test strips I had used.
Intestingly, the water is crystal clear. Like... glass clear. You can see the bottom of the deep end almost as though there's no water in it. The pool company left in their notes that the water looks "awesome" and "extremely clear".
Recently I started to keep much more detailed notes, but assume unless otherwise I added at least 10ppm's worth of chlorine a day. Here's what I have in writing:
6/23: Pool company
Reported: pH < 6.2, FC < 0.5, Alkalinity ~ 80, CYA 0 (This would have been after I had added 1 or 2 gallons of liquid chlorine earlier that day).
Added: 2 gal shock, 1 lb pH plus
6/29: Pool company
Reported: ph < 6.2, FC < 0.5, Alkalinity ~ 80, CYA 0 (same exactly as last time)
Added: 2lbs "yellow out", 1 lb ph plus, 2 gal shock, 1lb CYA.
6/30: Added 4 lbs ph plus. After several hours the pH was still below scale on test strips.
(Finally purchased a Taylor K-2006 kit so started using it)
7/1: 1:30pm
pH < 6.8 (bottom of scale) took 17 drops of R0006 to get to pH 7.4. According to book that means ~10 lbs of pH up should be added.
FAS-DPD: 2 drops to colorless (0.4ppm FC), +5 drops to pink again, 5-6 drops to colorless again (1.0-1.2ppm CC).
CYA: approx 90 (not 100% sure what it means by "black dot 'just barely' disappears" though).
+ 2 gal 10% liquid chlorine
7/1 7:30pm
Test strip: pH ~6.4, CC ~3, FC ~3-5.
TA: 13 drops = 130 ?
Added: 4 lbs pH up
7/2 9:00am
pH: ~7.2
FAS-DPD: 2 drops to colorless (0.4ppm FC), 2 drops to pink again (0.8ppm CC)
Added: 4 lbs pH up
7/2 11:00am
Added: 1 gal 10%
pH: ~7.5
7/2 1:30pm
pH: ~7.4
FAS-DPD: 7.5 ppm FC, 1.0 ppm CC (at this point I felt like some progress because it was the longest I'd ever seen it hold chlorine).
7/2 3pm: small pool party, 3 swimmers for about an hour.
7/3 9:30am
ph: ~7.4
Test strip: FC/TC off scale low.
TA: 80-120
Added: 1 gal 10% liquid
Noted water level was at 1/3 skimmer height so added about 45 mins from hose and now up to just over 1/2 skimmer height.
Summary
While the pH seems to be holding steady still seeing chlorine fall. We have had relatively little swimming this season and this chlorine will fall regardless of whether or not anyone goes in so I don't think it's swimmer contamination. Also, the pool is covered nearly 24/7 so it isn't contaminated by rain, nor does it receive UV light. Chlorine also drops down over night. Being that I didn't feel confident in the results from the test strips I was reluctant to add additional stabilizer in case lock was a problem. Recent tests with the Taylor show it to be in the 70-90 range now. I wouldn't also say we've seen "excessive heat" yet this summer - hottest day might have been 89 degrees and there have been quite a few cool days too. Finally, since the water seems so perhaps not an algae issue... unless there are 100% perfectly clear algae? The only thing I haven't formally done is a "SLAM", though I have been adding 3-4 gallons (or granule equivalent) per day.
Help!
Anyway... extremely long story short. What could this be, and what else should I do? I mean, the pool is very clear and comfortable to swim in, it's just that it seems that I have to continue to add a gallon of chlorine every 4-6 hours to keep it above 0.5.
Thanks (and sorry for the super long message).
FK
TL;DR: History
I have a rectangular in-ground pool about 3 years old, approximately 18,000 gallons. This was installed by the previous owner and this is the second season for me. It is chlorine, has a sand filter, retractable cover, chlorinator and UV filter. We keep the pool covered nearly all of the time, opening it when we swim and closing it afterwards. Last year the pool was maintained bi-weekly by the company that installed it, and they opened and closed it for the seasons each time. I had been doing the general chemical maintenance and checking last in between their visits and didn't really have any issues. This year they informed me that they just don't have the resources to do pool maintenance visits and to find someone else. Given my experience last year I figured I could handle it in the meantime while I found someone else.
This year when they opened the pool at the beginning of May after being covered since end of September it was pretty murky and teal colored. They added an algicide and a lot of shock and said to give it a few days and should be fine. It seemed to clear up after a few days though given the cooler spring the water just wasn't warm enough to swim so it got very little use in May. I did periodically test it with my test strips from the previous season but was getting somewhat erratic results so just figured they were no longer good and needed new ones.
During a particularly rainy week we were out of town for about 5 days and when I came back the pool was back to being murky and teal again. The PSI on the filter was 23 (should be max 20) and when I backwashed it, it had a noticeable smell. Afterwards the PSI was back down to normal. Over the course of a few steps, I added the recommended amount of HTC algicide, shock and clarifier and waited. After a several days it began to slowly clear up, however that's when the problem really started...
The problem (finally)...
In short, the pool does not and will not hold chlorine. Over the course of the past three weeks I have probably added 20+ gallons of liquid (10%) and 2 maybe 3 containers of granulated. Consistently after about 4-6 hours the free chlorine was down to below 1, sometimes looking like 0. The CC seems to remain proportional to the FC where when one is high the other is high and when low they both are.
I continued to pour 4 to 5 gallons per day seeing the same results. We brought in a new pool company and they reported on the first visit that the pH was also very low (below their lowest measurement on their strips). I had seen this as well but was very inconsistent across the different types/brands of test strips I had used.
Intestingly, the water is crystal clear. Like... glass clear. You can see the bottom of the deep end almost as though there's no water in it. The pool company left in their notes that the water looks "awesome" and "extremely clear".
Recently I started to keep much more detailed notes, but assume unless otherwise I added at least 10ppm's worth of chlorine a day. Here's what I have in writing:
6/23: Pool company
Reported: pH < 6.2, FC < 0.5, Alkalinity ~ 80, CYA 0 (This would have been after I had added 1 or 2 gallons of liquid chlorine earlier that day).
Added: 2 gal shock, 1 lb pH plus
6/29: Pool company
Reported: ph < 6.2, FC < 0.5, Alkalinity ~ 80, CYA 0 (same exactly as last time)
Added: 2lbs "yellow out", 1 lb ph plus, 2 gal shock, 1lb CYA.
6/30: Added 4 lbs ph plus. After several hours the pH was still below scale on test strips.
(Finally purchased a Taylor K-2006 kit so started using it)
7/1: 1:30pm
pH < 6.8 (bottom of scale) took 17 drops of R0006 to get to pH 7.4. According to book that means ~10 lbs of pH up should be added.
FAS-DPD: 2 drops to colorless (0.4ppm FC), +5 drops to pink again, 5-6 drops to colorless again (1.0-1.2ppm CC).
CYA: approx 90 (not 100% sure what it means by "black dot 'just barely' disappears" though).
+ 2 gal 10% liquid chlorine
7/1 7:30pm
Test strip: pH ~6.4, CC ~3, FC ~3-5.
TA: 13 drops = 130 ?
Added: 4 lbs pH up
7/2 9:00am
pH: ~7.2
FAS-DPD: 2 drops to colorless (0.4ppm FC), 2 drops to pink again (0.8ppm CC)
Added: 4 lbs pH up
7/2 11:00am
Added: 1 gal 10%
pH: ~7.5
7/2 1:30pm
pH: ~7.4
FAS-DPD: 7.5 ppm FC, 1.0 ppm CC (at this point I felt like some progress because it was the longest I'd ever seen it hold chlorine).
7/2 3pm: small pool party, 3 swimmers for about an hour.
7/3 9:30am
ph: ~7.4
Test strip: FC/TC off scale low.
TA: 80-120
Added: 1 gal 10% liquid
Noted water level was at 1/3 skimmer height so added about 45 mins from hose and now up to just over 1/2 skimmer height.
Summary
While the pH seems to be holding steady still seeing chlorine fall. We have had relatively little swimming this season and this chlorine will fall regardless of whether or not anyone goes in so I don't think it's swimmer contamination. Also, the pool is covered nearly 24/7 so it isn't contaminated by rain, nor does it receive UV light. Chlorine also drops down over night. Being that I didn't feel confident in the results from the test strips I was reluctant to add additional stabilizer in case lock was a problem. Recent tests with the Taylor show it to be in the 70-90 range now. I wouldn't also say we've seen "excessive heat" yet this summer - hottest day might have been 89 degrees and there have been quite a few cool days too. Finally, since the water seems so perhaps not an algae issue... unless there are 100% perfectly clear algae? The only thing I haven't formally done is a "SLAM", though I have been adding 3-4 gallons (or granule equivalent) per day.
Help!
Anyway... extremely long story short. What could this be, and what else should I do? I mean, the pool is very clear and comfortable to swim in, it's just that it seems that I have to continue to add a gallon of chlorine every 4-6 hours to keep it above 0.5.
Thanks (and sorry for the super long message).
FK
You can use 10 ml sample for your Taylor K-2006 FAS-DPD Free Chlorine (FC) and Combined Chlorine (CC) test. That will save you some reagent. Forget Test Strips!!!
