- Feb 27, 2010
- 86
- Pool Size
- 18300
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Jandy Truclear / Ei
Hello all. So my pool developed mustard algae, I think after the chlorine level decreased when I left town and with the heat and water evaporation, the water level went below the skimmer and warped some of the pipes, making the pump lose prime and stop working. The mustard algae, which I had once previously in another pool, was dust/pollen-looking stuff at the bottom of the pool when you brush the bottom (and no pollen-producing plants nearby), and I could get pollen-looking stuff again if I brushed a few hours later. In case it's relevant, it's been very hot here in South Florida recently.
I have been doing BBB, by the way, so I don't know if any other types of chemicals were added, but the pool had notably low CYA and calcium when I got it.
I did an OCLT (overnight chlorine test), and it went down from 4 to 2.5 (Fas-Dpd Titrating test). Chemistry was as follows:
pH 7.8
TA 95
CYA 70-75 (now 65-75 with some added water)
CH 370
CC 0.5
Salt 3400
So I decided to SLAM with liquid chlorine, targeting 29 per pool math, first bringing pH down to 7.2 (TA went to 85). The next day, there was no notable mustard algae when brushing the pool. The water is (and was) clear. There are no ladders or things like that in the pool that could have algae trapped behind them, and I've taken all the lights out of their sockets. I opened and brushed the hole for the umbrella. I've opened the cleaner line and propped open its door to have SLAM-level chlorine flowing through. I cleaned the filter, which was clean-looking.
I have yet to get the suggested 1 point FC loss on the OCLT to proceed to mustard algae FC levels for 24 hours. I've been brushing and vacuuming daily, and I've left my robotic cleaner brushing and vacuuming the pool all day. FC results are as follows:
Day 1 night : 32
Day 2 morning: 29
Day 2 night : 34
Day 3 morning: 28.5
Day 3 night : 30
Day 4 morning: 27
Day 4 night : 30.5
Day 5 morning: 23.5
Day 5 night : 29.5
Day 6 morning: 24.5
Day 6 night : 29
Day 7 morning: 24.5
Day 7 night : 30.5
Day 8 morning: 26.5
For one thing, I check the chlorine levels around 7 AM. There is light out but no sunlight on the pool (at that hour the house shades the pool anyway). I assume the indirect light at that hour wouldn't yet cause any notable extra chlorine loss.
The second thing is - I failed to find any post discussing whether the "1 point FC loss rule" holds as the target FC level increases. My CYA is at most 75, which is around what is recommended on this forum for an SWG pool. But it's clear that the higher the FC, the more you lose - it's more a percentage of the FC level than an absolute FC loss. I started SLAMming for a FC loss of 1.5 in the presence of clear mustard algae, which was a 38% loss. Now i have 4-5 point FC loss nightly, which is around a 17% loss - much better percentage, but much higher absolute number. The mustard algae has not been visible, the pool is clear, and the CC is <1 since day 1, so it seems logical that what’s important is the % FC loss rather than an absolute number.
I would appreciate any thoughts on whether I should do something differently. Looking forward to hearing your thoughts. Thanks!
I have been doing BBB, by the way, so I don't know if any other types of chemicals were added, but the pool had notably low CYA and calcium when I got it.
I did an OCLT (overnight chlorine test), and it went down from 4 to 2.5 (Fas-Dpd Titrating test). Chemistry was as follows:
pH 7.8
TA 95
CYA 70-75 (now 65-75 with some added water)
CH 370
CC 0.5
Salt 3400
So I decided to SLAM with liquid chlorine, targeting 29 per pool math, first bringing pH down to 7.2 (TA went to 85). The next day, there was no notable mustard algae when brushing the pool. The water is (and was) clear. There are no ladders or things like that in the pool that could have algae trapped behind them, and I've taken all the lights out of their sockets. I opened and brushed the hole for the umbrella. I've opened the cleaner line and propped open its door to have SLAM-level chlorine flowing through. I cleaned the filter, which was clean-looking.
I have yet to get the suggested 1 point FC loss on the OCLT to proceed to mustard algae FC levels for 24 hours. I've been brushing and vacuuming daily, and I've left my robotic cleaner brushing and vacuuming the pool all day. FC results are as follows:
Day 1 night : 32
Day 2 morning: 29
Day 2 night : 34
Day 3 morning: 28.5
Day 3 night : 30
Day 4 morning: 27
Day 4 night : 30.5
Day 5 morning: 23.5
Day 5 night : 29.5
Day 6 morning: 24.5
Day 6 night : 29
Day 7 morning: 24.5
Day 7 night : 30.5
Day 8 morning: 26.5
For one thing, I check the chlorine levels around 7 AM. There is light out but no sunlight on the pool (at that hour the house shades the pool anyway). I assume the indirect light at that hour wouldn't yet cause any notable extra chlorine loss.
The second thing is - I failed to find any post discussing whether the "1 point FC loss rule" holds as the target FC level increases. My CYA is at most 75, which is around what is recommended on this forum for an SWG pool. But it's clear that the higher the FC, the more you lose - it's more a percentage of the FC level than an absolute FC loss. I started SLAMming for a FC loss of 1.5 in the presence of clear mustard algae, which was a 38% loss. Now i have 4-5 point FC loss nightly, which is around a 17% loss - much better percentage, but much higher absolute number. The mustard algae has not been visible, the pool is clear, and the CC is <1 since day 1, so it seems logical that what’s important is the % FC loss rather than an absolute number.
I would appreciate any thoughts on whether I should do something differently. Looking forward to hearing your thoughts. Thanks!
Last edited: