Chlorine demand

[mikefamig]

From what I've learned here and supported by reading at other sites, the ideal level of CYA is 40 - 50 ppm. I called Taylor to confirm this and they insisted that I should not go above 50 ppm of CYA in my vinyl pool using Sodium hypoclorite sanitizer. I am currently testing between 40 and 50 ppm and the Taylor rep told me that is perfect and to leave it alone.

I just did a careful OCLT and lost a little less than 0.5 ppm FC. The water is clear and sparkling and everything is perfect except that the pool is using 5 - 7 pints of 12.5% shock per day in order to maintain 8 ppm free chlorine. Again, my CYA measures between 40 ppm and 50 ppm and I have been calling that 50 ppm.

Granted the pool is in direct sunlight but this still is high compared to claims made here. I added about 1 pound of granular CYA and will see what happens in today's sun.

Now to my question - Am I alone with this kind off demand? The water looks and tests to be is as clean as it's ever been.

Mike.

 

[Richard320]

How many gallons is your pool? Is it 2' deep? 8' deep? Sloped? Or is it 16' diameter and 42 inches deep? In essence, what does 5 - 7 pints of 12.5% translate to in parts per million?

 

[mikefamig]

My sig file shows 16' x 32' foot in-ground but I failed to mention that it does have a deep end and I estimate it to have nearly 20k gallons based on arithmetic and the fact that a gallon of 12.5% adds about 6ppm.

Mike.

 

[Richard320]

5 pints is 80 ounces and in a 20,000 gallon pool that adds 3.9 FC. That's high. If you've been needing 7 pints, that's way too high. It could be

1) Nascent Algae Bloom
2) High usage
3) High sun losses
4) Old bleach that isn't as strong as you think.

The OCLT seems to have ruled out Algae. Have the kids been in the pool a lot, maybe with their friends? Maybe with a bunch of pool toys that keep flying in and out, bringing contaminants with them? Solar losses are being addressed by your addition of more CYA. Which leaves bleach. Check out Chlorine Date Code Decoder/Easy Way to Measure Strength.

 

[mikefamig]

The pool has had no use all week.

I've questioned the consistency of the chlorine that I use. I buy it at Ocean State Jpb Lot and there is no date code on it but there are users here that also use it and have had good luck. I have also added some and tested shortly afterwards and it as been good.

The pool gets about ten hours of sun but this is still a lot of chlorine to use.

I'm thinking that the problem is the line of 25' tall White Pine trees in the neighbor's yard very near the pool. This is my first full year using the TFP method so I have nothing to compare to.

I would try a back-wash but it has been dry here and I have a well which I like to go easy on so I keep the back-washing to a minimum.

Mike.

EDIT - On second thought, if I had something bad trapped in the filter it would show up in the OCLT so a back-wash wouldn't help.

 

[mikefamig]

The chlorine loss turned out to be mostly due to the sun. I added a little CYA which now tests to be a solid 50ppm or a little more and it made a big difference. It was sunny on Friday and I used a little over 2 ppm for the day and the past two days have been overcast but again the chlorine loss is only a few ppm/day.

I'm surprised what a big difference just 10 ppm of CYA has made.

Mike.