High CYA (90-100ppm) - keep chlorine up or drain?

[MoogMan]

Hi all!

I’m pretty anal regarding the pool (10000 gallons) and test daily, I’ve maintained a pretty perfect balance since opening but after a few heavy rains, heavy recent use (kids splashing) and an accidental overfill (forgot I left the faucet in when topping up!) the CYA diluted from 70ppm to around 40.

So decided to add 30ppm CYA back but looks like I got my measurements wrong as I’m now sitting at around 95. Oops.

The pool will be seeing moderate to heavy use over the next few weeks, and will no doubt need a few inches of water added soon which will help dilute. We are in the 80s here in NC and the pool receives with full sun daily.

I was thinking I’d be okay keeping the chlorine up at the higher range (8-12ppm) and waiting for the CYA to drop as the water dilutes.

Do you think this would work or should I drain?

Thanks.

Fiberglass SWG pool
10000 gallons

FC: 8
TA: 70
PH: 7.7
CH: 300
CYA: 95

 

[ajw22]

Have you done the CYA dilution test to confirm your CYA is 90-100?

For CYA > 90ppm, repeat the test adjusting the procedure as follows:

1. Fill the mixing bottle to the lower mark (15 ml line) with pool water.
2. Continue filling the mixing bottle to the upper mark (30 ml line) with tap water.
3. Shake briefly to mix.
4. Pour off half of the contents of the mixing bottle, so it is again filled to the lower mark (15 ml line).
5. Continue the test normally from adding R-0013, but multiply the final result by two.

If you need to dilute the pool water further then apply these ratios:

Pool water	Tap or distilled water	Multiply result by
1	1	2
1	2	3
1	4	5

Note that when doing a diluted test not only do you multiply the range of the test you multiply the error rate of the test, so results are a ballpark - not an absolute.

 

[MoogMan]

Hey there!

Thanks for the reply. With the diluted test I get approx 45, so it seems that would tally with the 90 result I got today.

 

[ajw22]

Then I would just maintain your FC level for your CYA and things will adjust over time.

 

[MoogMan]

Thank you, appreciate your help!