Mysterious sharp increase in CYA

What is floc, clarifier, stabilizer, cyanuric acid,
algaecide, brightener, dichlor, sodium hypo,
sodium bisulfate, ....??
Ziora
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Mysterious sharp increase in CYA

Postby Ziora » Tue 24 Jul, 2007 21:30

20,000 gal. in-ground, vinyl liner, sand filter.

I don't have a good test kit yet. I have been using a 3-way to get a pH reading, 6-way test strip (worthless, unless I want to get my chlorine above 10), and a small pool company I have to come to trust more than others.

Today's readings:

TC: 2
FC: 2
pH: 7.4
CH: 25
TA: 105
CYA: 40

The FC is 2 because I didn't think my CYA was so high. I put 4 oz. more of PolyQuat 60 in last night to be safe.

A few weeks ago, the CYA was 10. I added 8 oz. of the Dichlor twice a day for 3 days and once a day for 3 days because I wanted to raise the CYA to around 25. I took the water to be tested today, thinking it would be no higher than 20.

I asked the guy how that was possible to be so much higher when I haven't added that much of the granular. He gave some kind of explanation that didn't make sense.

Is it possible for the CYA to be somehow latent, until certain conditions are met? Is it more likely they have made a mistake either times they tested my water? Everything else seems to be close to my results.


chem geek
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Postby chem geek » Wed 25 Jul, 2007 02:34

You added 8 ounces of Dichlor (I assume the dihydrate type) 9 times so that's 72 ounces which in your 20,000 gallon pool would raise the CYA level by 13.6 ppm (and your Free Chlorine by 15 ppm, though spread out over the 6 days).

The CYA test isn't perfectly accurate so may be +/- 10 ppm so starting from 10, adding about 14 ppm, then measuring 40 is a stretch, but I'm guessing the testing wasn't done consistently. You'd probably get more consistent and accurate results doing the CYA test yourself using a good test kit (such as the Taylor K-2006). The test at the pool store may be using a light meter for measuring the turbidity which in theory should be more accurate, but it may not be calibrated or the person doing the test may not have mixed thoroughly or used the wrong amount of reagent, etc.

It is true that CYA added to the pool from pure Cyanuric Acid takes a long time to dissolve so it can continue to build up, but this is not the case with Dichlor which dissolves very quickly.

Richard
Backglass
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Postby Backglass » Wed 25 Jul, 2007 08:23

Yet another reason to not use strips or trust the kid behind the pool store counter.

Real pools need a real test kit.
===============================
I'm no expert...just a long time pool owner. The real experts are at www . troublefreepool . com

Download Bleachcalc free at troublefreepool . com /files/BleachCalc262.exe and start saving money on chemicals.
Ziora
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Postby Ziora » Wed 25 Jul, 2007 12:37

I bumped up my FC to 7.1 last night, using the bleach calc. for dosing amounts. The pool has been losing about 2.5ppm chlorine during the day, and I don't want it to drop below 4.5. Am I right to assume if I start to see more of a chlorine loss, the CYA is probably not as high as 40ppm?

I know I need a good test kit. It's on my birthday wish-list. I used to ask for jewelery :)

BTW...Kroger has 3qt. ultra bleach on sale for $1. I grabbed a dozen jugs and it was kind of creepy the way people looked at me. One guy in line behind me half-jokingly asked if I was building bombs. I explained why since I don't want anyone thinking I'm doing something fiendish. Sheesh.
Backglass
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Postby Backglass » Wed 25 Jul, 2007 13:00

Ziora wrote:Kroger has 3qt. ultra bleach on sale for $1. I grabbed a dozen jugs and it was kind of creepy the way people looked at me. One guy in line behind me half-jokingly asked if I was building bombs. I explained why since I don't want anyone thinking I'm doing something fiendish. Sheesh.


Just FYI, you did the right thing as large purchases of bleach are also a warning sign for a meth lab. :shock:
===============================

I'm no expert...just a long time pool owner. The real experts are at www . troublefreepool . com



Download Bleachcalc free at troublefreepool . com /files/BleachCalc262.exe and start saving money on chemicals.

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