CYA levels before (mustard?) SLAM and other questions

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SuddenPool

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Bronze Supporter
Oct 24, 2016
26
West Lafayette, IN
Hi folks,

I had gotten my pool to clear levels last month, but because of travel and related negligence in the last few weeks, allowed FC levels to drop really low.

Now I notice clumps of algae formation (yellowish tinge) in some corners of the pool.

Current readings are:
FC: 0
CYA: Not registering on the kit - which means < 20
TA: 170-180
pH: Was 8.2, but I've now brought it down to closer to 7.8

The interesting thing about CYA is that when I opened the pool for the summer, CYA was similarly low/absent, and I had added stabilizer (using the sock method) and brought it to 30. Now it's apparently gone again?

We have had 6 inches of rain (thunderstorms!) in June, and another 6 inches in July. It really throws off my pH.

Anyway, clearly I need to do a SLAM. Given the yellowish tinge, I'm fearing it is mustard algae and need to use higher FC levels for the SLAM.

So I have all these questions now and hoping someone can help with guidance.

1. Is it expected/surprising that CYA levels have dropped over time?

2. Should I increase the CYA levels to 30? more? before starting the SLAM?

3. Should I also actively try to further reduce pH with muriatic acid before the SLAM?

4. I'm a bit concerned about the "hiding places" of algae. This is an old pool and there are some parts like an old non-functioning underwater light, and the plastic steps - how can I clean them - not even sure the underwater light fixture can be moved/dismantled for cleaning?

5. I also went to using Zeofiber in my DE filter when I opened the pool. This means my filter runs at higher psi than "normal". Is this because of the new type of filtering agent? Or the fact that there's algae?

Thanks for any help.
 
Hey Suddenpool!

1. No, it is not surprising. CYA level will decrease with dilution (like rain water), splash out. When did you open your pool?

2. Yes. It is usually good to have the CYA around 30ppm for the SLAM process. While the shock FC level is a little higher with the higher CYA, you will lose less FC to the sun and will thus actually use less bleach during the day. You certainly need > 0ppm of CYA because if you have none in the pool, you will lose 50% of the FC to the sun every hour in the middle of the day.

3. Yes, it should be easy to add some MA to lower pH to 7.2-7.5. Bleach is more effective at low pH so aiming lower initially will give you every advantage.

4. Brush, brush, brush. You have to expose any algae to CL.

5. Sorry, I do not know anything about Zeofiber.

Good luck!
 
5. Most likely it is algae. Nothing clogs up a filter than algae. We recommend cleaning or backwashing the filter when pressure rises 20-25% above clean pressure.
 
Thanks OTPirate and pooldv!

One question about the SLAM process - I think I'm supposed to monitor it every 2-3 hours and "top up" FC levels to the SLAM value if it has fallen off, right? But for my situation, the SLAM FC level is 24 ppm. This is way more than the test-kit's Cl PPM level indicator. How can I measure/monitor high FC levels?
 
I had added 4 gallons of 8.25% liquid bleach at around 11am today (was expecting it to go to 20+ ppm after that). Did not measure the FC.

In the evening at around 7pm, the FC measurement was 5, and CC was 1. CYA is still too low to register (it's been dissolving in a sock since this morning).

Is it possible to lose this much FC to sunlight because of low CYA levels?
 
Absolutely possible to lose that much ... with 0 CYA, I would have expected it to all be gone if you have a lot of sun exposure.

Start squeezing and massaging that sock ;)
 
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