First results with TF-Pro

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With such a high CYA, have you repeated the test to verify?
That high of a value didn't happen overnight unless someone dumped excessive amounts of CYA in the Pool. With a low chlorine value to CH to CYA ratio, you would have had algae issues for several years if the CYA source was Tabs,
 
BMerrill said:
With such a high CYA, have you repeated the test to verify?
That high of a value didn't happen overnight unless someone dumped excessive amounts of CYA in the Pool. With a low chlorine value to CH to CYA ratio, you would have had algae issues for several years if the CYA source was Tabs,
Click to expand...
I repeated the test a few times. I diluted the pool water with distilled water at a ratio of 1:3, got a result just over 100, and multiplied that by 4.
The pool has been maintained using Tri Chlor tabs for 4 years (since we bought the house). That being said, for the first 2 years we used a pool service. I don’t what else they used besides the Tri Chlor. I do know that they “shocked” the pool at least a few times during that period. It was last drained about 3 years ago, when we had the pool decking re-done.
For the past 2 years I have been managing the pool myself, using Tri Chlor tabs and test strips. Sometimes I would get a fair amount of algae for brief periods. I would scrub the pool, back flush the filter, add a gallon or so of liquid chlorine, and up the tablets. That would generally take care of it, at least to my eye.
This year, as the weather started to warm up, I noticed some different test results on my strips. Namely, low pH and high TA. In the process of researching how deal with this, I ran into TFP, learned about the CL/CYA relationship and so on. I bought a proper test kit, and have been using strictly liquid chlorine for about 2 weeks. I have been maintaining the FC level around 9.5, which I’m sure is higher than it typically was when I was using tabs. I know that this is way below the recommended level. My thinking was that I would increase the level an little, and see what that did. But I didn’t see the point in dumping a crazy amount of chlorine into the pool, knowing that the first order of business was a water exchange, and I would be doing that soon.
That being said, even increasing the FC to 9.5 has helped, and the water looks very clear, to my eyes. My spouse was usually the first to notice when algae started to develop, and she thinks it’s looked great for the past 10 days or so. This is strange since, according to PoolMath, I am nowhere near the appropriate FC level based on my CYA level.
 
No drain water exchange was done. The GPM on my pump was 4.8. I ran it for around 49 hrs, so took out around 14K gallons.

Test results today:

FC - 0.5
pH - 7.8
TA - 150
CH - 275
CYA - <30

I started by adding 35oz of dry cyanuric acid (sock in skimmer). In pool math, I said the CYA was at 20, and I wanted to bring it up to 40. I think it's probably lower than 20 in reality. Next, I added 109oz of 10% bleach, to bring the FC level to 7. Next, I plan to add dry acid in order to bring down pH/TA, and then aerate to bring pH back up.

I am thinking I will leave CH alone, since it is on the low side of recommended range, and will go up with evaporation.

Am I on the right track here?
 
Dry Acid is Sodium BiSulfate. When you use it, the sulfates remain in the water. As they build up in your water, they are corrosive to metals, cement, plaster, etc. In your environment, where we have very little water turnover, except when you do a complete drain(which you hope to not do very often), the sulfates can be an issue.

See Acid - Further Reading
 
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mknauss said:
Dry Acid is Sodium BiSulfate. When you use it, the sulfates remain in the water. As they build up in your water, they are corrosive to metals, cement, plaster, etc. In your environment, where we have very little water turnover, except when you do a complete drain(which you hope to not do very often), the sulfates can be an issue.

See Acid - Further Reading
Click to expand...
@mknauss Thanks so much for all the advice.
 
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