Can my CYA really be that low?

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Fronzizzle

Fronzizzle

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Jun 29, 2017
87
Augusta Township, Michigan
Hello all,

I have an above ground, approximately 13,500 gallon pool. For the last couple of years, we were using chlorine tablets instead of liquid. At the beginning of last year, I had some issues so I really studied up (and posted on here often) and got the pool as clear and clean as it's ever been.

We switched to liquid chlorine, but our CYA basically stayed borderline high all season, around 60 ppm.

When we closed the pool in the fall, we drained maybe 1/3 of the water, but probably less. We opened it this weekend and finally finished filling it this morning. I checked the pH (it was 7.6) and then the CYA, and I'm basically getting nothing - with the tube filled up all the way, I can still clearly see the black dot. It's probably not 0, but it's below the threshold of the test. Is this possible?

I'm using a Taylor test kit, and I did notice that the reagent is expired. Could that be the issue? Certainly I know it's not ideal, but wondering if it could be bad to the point of not give me any results?
 
CYA reagent is very stable unless it is contaminated or has been frozen.

Your CYA can drop over the winter due to dilution and it can also naturally degrade. You stated your pH was 7.6, that is good. Did the water have any CC? What does the water look like?
 
My CC is 0.5 ppm.

For a lack of a better term, the water is murky or maybe a little cloudy? Not green, but not clear like last year. I just got the filter going this morning, so I haven't vacuumed it fully yet (lots of dirt and dead worms on the bottom).

I plan on SLAM but not sure if that's enough to take care of the murkiness?
 
A SLAM will cure the murkiness.

Whenever someone presents with no CYA that had it before close, we get concerned about ammonia. For a test, prior to adding any CYA, add enough liquid chlorine to raise your FC to 10 ppm. Circulate the pool for 15 minutes and test FC and CC. Report the results here.
 
No problem. If the pool holds chlorine, you do not have ammonia.

Add 20 ppm worth of CYA using the sock method. Assume your CYA is 30 ppm and use SLAM level FC of 12 ppm. Do not go way over that, it can damage your liner.
 
Quick update and another question:

The water looks great today - basically crystal clear. I'm going to continue with the SLAM, though, because I'm getting debris on the bottom and in the filter still (more than normal). I'm thinking one more day and I should be good, maybe two. So thanks again for the advice.

For the question, I know this has been asked before (probably by me) but I can't seem to find my post. Knowing I add chlorine by hand and the SLAM target is 12 PPM, does that mean I should be adding chlorine when it gets to 12 PPM (so, say, enough to take it to 16 ppm and let it come back down), thus never getting below 12 PPM, or do I hit it when it gets down to, say, 8 ppm and then bring it back up to 12 ppm?
 
Raise you FC back to 12 ppm when you test. It is best to not go too far above 12 ppm as it can damage your liner. This is with a CYA of 30 ppm.
 
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