Post-refill, next steps

[brunoforestier]

I've partially drained and refilled my pool three times over the last 2+ weeks, to solve a high (roughly 250ppm) CYA problem. Other stats prior to first drain:

TA 104 (not sure how I came to this number since the K2006 kit only goes in multiples of 10)
FC 2.4
CC 0.4
pH 7.4
CYA ~250
CH didn't measure

After three partial (40%/40%/60%) drains/fills:

TA 100
FC 0.6
CC 0.8
pH 7.9
CH 170
CYA ~10 (test kit black dot didn't disappear, but was somewhat starting to?)

I'm not sure how to measure CYA when the test kit doesn't measure below 30ppm. Also, I measured CYA before the third and final drain, which showed 105ppm. A 60% drain/refill should bring that to roughly 45ppm -- any thoughts on what's going on with the CYA?

Additionally, I am using the Pool Math app. It's telling me to lower the TA, raise CH. However, the Taylor 2004B guide indicates the CH and TA are within acceptable ranges.

I'm trying to make sense of what to do next here, and have digested a lot of information over the last few weeks. I've read all of the balancing guides here and have read the relevant portions of the 2004B guide, and I'm not really clear what I should do next.

One last thing: Does the indoor pool aspect change things? I think I read that 20 CYA was fine for indoor. How do I measure CYA accurately for under 30ppm?

 

[setsailsoon]

Bruno,

Welcome to TFP! You need to raise the FC level next. Use the chart below and Pool Math to calculate the amount of liquid chlorine required. As you probably know we recommend using liquid chlorine or SWG instead of tablets because they cause build up of CYA that interferes with disinfection.

CYA is the most difficult test so you may be off a little in your readings. You'll get more consistent with practice and the test is still more reliable than pool store "free" tests. It works best if you are outside with your back to the sun and look away from the container before you check the dot. As soon as the dot is gone when you first look down you are at the CYA level, Remember always round up. You are correct that low levels are all that's required for indoor pools. Also, are you sure the volume of your pool volume is correct?

I hope this is helpful.

Chris



FC/CYA Levels

 

[brunoforestier]

Fantastic question! I have a very oddly-shaped pool, and I don't have precise details about the various depths of the deep end. However, using the measurements I do have (deepest point = 10 feet, all exterior dimensions, exact measurements of shallow end depths), I feel pretty confident that I'm not off by more than a few thousand gallons.

are you sure the volume of your pool volume is correct?

 

[brunoforestier]

The pool math app suggested 96oz of 10% liquid chlorine to bring the FC to 3.0. My FC measurement after adding the 96oz and waiting 12 hours shows 1.2 FC.

Does anyone have guidance around the differences I highlighted above between the Taylor guide book and the pool math recommendations? Is Taylor out to lunch?

 

[setsailsoon]

When did you test? If that was overnight you have algae. If you tested in the morning that's fairly normal drop this time of year for chlorine loss. Until you get things figured out I'd shoot for the high end of the target (5 ppm FC). Not sure about the Taylor guide - never read it but a lot of pool "experts" ignore the CYA/FC relationship. Please take a reading one hour after adding your chlorine with the pump running.

Chris

 

[brunoforestier]

For the test results I shared earlier today, I tested 12 hours after applying the 96oz of chlorine.

My latest test (just now) showed 0.6 FC and 7.7 pH. I added another 128oz of the liquid chlorine and will re-test in an hour.

Is there a better scientifc-based approach at this point? This seems like a lot of trial and error. Do I need to just SLAM the thing? I feel very lost at this point, as there is an abundance of information but no clear path to solve the problem I'm seeing. Appreciate the feedback!

 

[brunoforestier]

5.6 an hour after the 128oz of 10% liquid chlorine

 

[brunoforestier]

5.0 FC and 7.8ph just now.

any suggestions on next steps?

 

[brunoforestier]

As a recap, here's my current test results (pH and FC measured just now):

FC 5.0
pH 7.8
TA 110
CH 180
CYA 10 (estimate, not sure how to measure under 30)

Am I over thinking this? Do I just need to add muriatic acid to lower the pH and TA? I have done additional reading around TA and carbonate alkalinity, but don't see a lot of guidance here to worry about the carbonate alkalinity.

 

[brunoforestier]

FC down to 4.2 just now. This means it’s actively “eating” something like algae? Again, I feel very lost as to how to proceed here. Would like to start using my pool soon!

 

[azxd09]

If your CYA is really 10, then I would not expect any of your FC to last more than a few hours in the sun. Could this be what is causing your drop? I also just did a drain and fill and am having a similar issue. I added some CYA (based on poolmath), and I calculate that I am around 20ppm right now, but am also going to rely on 2 weeks of some trichlor tabs to get my CYA up to 30. I don't lose any FC overnight, but it is all gone by 9-10AM with 3 hours of sun by that time. That said, I am in AZ with intense sun, but I assume 10ppm of CYA is probably too low anywhere. Just my $0.02, maybe others can comment on whether 10ppm might be ok in other regions?

 

[brunoforestier]

Indoor pool here, so while there is some sun coming in through the windows, it's quite limited.

I'm starting to think I should add CYA until it's 30, just to be "in line" with what most people are used to dealing with.

 

[azxd09]

Ahh, sorry, my bad, I didn't catch the indoor part. You're right, should not be an issue with an indoor pool.