CL is flat lining

[Richard320]

For a variety of reasons outside my control, I am still stuck with very high CYA. 140 consistently. So I keep CL high - 12 to 16. In anticipation of leaving on vacation, I let CL drop so I can get an accurate pH. Then I'm gonna shock it before I go.

4/9 CL 16
4/11 CL 13
4/12 added 1/2 gallon 10%
4/15 CL 12.5
4/17 CL 11
4/19 CL 11

I have added quite a bit of acid to keep pH down and reduce TA, but no Chlorine for a week. Typically it works out to using about a quart a day, in full sun. All the sudden, it just stopped dropping. Does Chlorine flat line because of the CYA? Is this as low as it's gonna get? The water is crystal clear.

On a side note - would this be a way to tell what the CYA level is?

 

[JasonLion]

No, the FC level should continue coming down. I noticed that you wrote it as CL, as you testing FC, CC, or TC? If your test measures TC, you might have a very high CC level, which won't go down on it's own (though that seems unlikely).

 

[Richard320]

No, the FC level should continue coming down. I noticed that you wrote it as CL, as you testing FC, CC, or TC? If your test measures TC, you might have a very high CC level, which won't go down on it's own (though that seems unlikely).

It's stalled on 11 FC. CC = 0. TC = 11

Plane leaves later tonight, so I dumped a gallon in, which should push it up to 17.

 

[Melt In The Sun]

I was under the impression that high pH readings were caused by chlorine levels that are high relative to your CYA, not just high numbers. ie. 16 ppm FC is shock level at CYA=40 (giving erroneous high pH #s), but is in the recommended range for CYA=140 (thus would give an accurate number).

Jason, is this correct?

 

[JasonLion]

High FC levels cause problems for the PH test regardless of the CYA level. With FC up to almost 20 the PH results are only off a bit (more the higher FC goes, but not way off), somewhere a bit above 20 they switch to way wildly wrong.