Low to little CYA


Well-known member
Apr 29, 2018
Cos Cob CT
Hi all - Been doing "TFP" since last spring & test chlorine via DPD method.
We live in sw CT. Weather's been up & down. Water temp is down to 73 due to cooler weather; entire pool only gets sun from approx 9 am - 2 pm, with a tiny portion getting sun til 4. Hardly using pool (once a week, 8 & 10 yr olds in it for hours, for now until summer)

So far, no issues. Opened to crystal clear water. I keep pool at high end of range via math calculator. Did mini-slam once due to dead mouse in skimmer the other day. CC has been 0 daily since opened.

Last year we used a few trichlor pucks once to raise CYA. Presently I'm not sure the new bottle of R-0013 is good so ordered another & should have that soon. (I've bought "bad" reagents in the past so want to wait if possible to ensure what the CYA is before hitting the pool with stabilizer. The test is always difficult to perform, especially as I need reading glasses. Very awkward squirting solution to the tube at waist level, drop by drop! lol. The sun is out today, so retested & still no disappearing dot even with larger tube that goes to 20 (I have proper mixing bottle for that tube). Therefore, I wait for newer R-0013 to confirm what I think cya might be (between 10-15) before adding stabilizer.

QUESTION: If I do have 10-15 ppm cya, wouldn't pool be eating a lot of LC daily? It's only been needing LC every other day at present. Is this due to little swim load, cool air & water temp, & being mostly in the shade? Or am I fooling myself & a bloom is soon to explode? As soon as I confirm cya, I'll perform overnite test to ensure all is ok & slam not needed.

I'm out of trichlor pucks so will get some & put 3 in the feeder until I can retest cya, but would like to know why my chlorine isn't being eaten up with such a low cya...
FC 5 (range is 3-4)
CC 0
CYA ? very low as can still see dot at 20 pmm in larger tube
PH 7.8
TA 50
TEMP: 74º


Last edited:


Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
Laughlin, NV
R0013 is the most stable reagent. Should last years if kept in climate controlled environment.
When you do the CYA test, try this next time.

Once you have your solution ready, back to the sun, etc. Fill the vial to a line, say 80, lower the vial to your waist level and glance for the dot, you see it, add solution to the 70 line, glance, see it, repeat until you no longer see it with a glance. Then use the CYA value one step above the line you read. So if you stopped at 50, use 60 ppm CYA.

The vial is in logarithmic scale. So it is not viable to interpolate between the lines. Just use the whole numbers, such as 50, 40, 30, ....


Well-known member
Apr 29, 2018
Cos Cob CT
Tks! That's pretty much how I do it, except for the glancing. Just spoke to Wayne at Taylor & he also assured me that the R-0013 is very stable & would turn milky if bad. So about to get some trichlor pucks for the auto feeder to raise the cya as we did last year! But will try your "glance" method first! (test kit & pool photos now added OP) Tks again!