Chemistry confusion - new member - old pool

[MikeA47]

I just got my Taylor 2006 kit and recorded the following numbers
FC 2.0/CC 0.2 = TC 2.2
PH 7.4
TA 120
CH 300
CYA 0
This is the first time I have personally tested our pool in years.

Our pool was filled in 2010 and is covered with a vinyl pool cover >95% of the time.
The pool guy has been doing the chemistry and most of the chlorine added is
via a Pentair Rainbow 300 offline drip feeder. Supplemented with liquid chlorine and
acid as needed.

What confuses me is the 0 value for CYA. From reading the forum shouldn't the use
of tricolor in a feeder cause the CYA to continuously increase due to stabilizer in the tablets
until you have to drain water to get it back in range? I am having the opposite problem, and
have 0 CYA using tricolor tablets.

All this is in preparation for adding a liquid chlorine feeder, probably the Stenner pump approach,
which seems the most bullet proof. Can't use SWG, though I would love to, because we have a
cover with metal rails installed below the coping, and also travertine natural stone for coping and deck.
Evidently the heightened salt content would not be nice to these items.
The automatic chlorinators, such as Intellichem, don't get good grades for reliability, and the
ozone/uv systems like Solar Eclipse don't seem to work at all in outdoor, low usage pools.

Hope I am making sense.
Thanks for any inputs
Mike

 

[tim5055]

Welcome to TFP!

Yes you make sense and I agree with your confusion over the CYA. Have you had any "events" recently that allowed hour FC to drop to 0 recently? The only posibilitys I can come up with is testing error or bacterial conversion of the CYA.

 

[MikeA47]

No events that I am aware of, just infrequent replenishing of the pool water. Maybe 1" per week.
I was thinking that maybe our low usage pattern coupled with a cover that is almost always on the pool was somehow
causing the CYA to be so low.

I will retest and see if I get a different reading.

Thanks
Mike

 

[Divin Dave]

Hi Mike,
That is a bit perplexing.
However, I would trust the Taylor test kit. If it says 0, then thats what it is...

I tell ya though, especially since you're in CA, consider yourself very fortunate that you wont have to face the possiblity of draining your pool or managing FC with extremely high CYA. A lot of folks right now arent as fortunate as that.

 

[MikeA47]

Well, I will just be happy with my luck. I did a retest with the same result. Maybe not CYA=0, but the water was almost
clear with the solution added. Put 7ml of pool water in the test tube, added 7ml of R0013 reagent as directed, shook
for 30 seconds. After filling the viewing tube all the way (just past the 30 ppm mark), the black dot on the bottom
was still completely visible, and the water+reagent was almost clear.
I will stay with my trichlor tablets, and drip feeder, a bit longer before I go to the hassle of converting to a liquid chlorine feeder. I'll keep
an eye on the CYA level in the meantime. I suppose I do need to get both the FC level up a bit, to 3 or so, and definitely have to get the
conditioner (CYA) to a level of 30 or so.
Thanks for the quick replies.
Mike

 

[Divin Dave]

That sounds like a great plan Mike.