CYA and Dichlor

Jerry Lee · May 23, 2013

First off this is my second year with BBB and I couldn't be happier. Upon opening my pool I had test results of...

ph- 7.5
fc- 0
cc- 0
ta- 110
ch-280
cya- < 20

I added the recommended amounts of bleach and in 1 day the pool was beautiful. However with CYA of less than 20 the chlorine has been sucked out pretty rapidly. I had some dichlor left over that of course I don't use anymore so I added 5- 1lb bags to raise the FC and the CYA. The question is, Do I wait a week to retest CYA? Or will using dichlor immediately raise the CYA by 11 (according to the calculator). I've been adding 121 0z. of 8.25% nightly and by the next day, it is gone. The one day I didn't do it, the water turned cloudy. Tested for CC's again today and still nothing.

Thanks!

JasonLion · May 23, 2013

No, when using dichlor you can retest CYA after 30 minutes with the pump running.

If you are losing chlorine during the day, that is normal. But if you are losing chlorine overnight there is a problem.

Butterfly · May 23, 2013

Yep, right away (or within 30 minutes to an hour anyway).

But remember the CYA test is +/- 15 .

Jerry Lee · May 23, 2013

Thanks guys.... Had to order some more reageant from Dave for the CYA test. I'll just keep adding bleach daily until it arrives and before I think about the doing the OCLT.

spidey07 · May 23, 2013

You have zero FC in your pool so letting it dip that low is inviting something to grow. The OCLT is a good way to tell if you need to shock or not or if you've got something growing in your pool. I'd perform one as soon as possible given your water turned cloudy when you let your chlorine drop.

It doesn't take long, it can happen during one day for algae to take hold even if there are no visible signs.

Dose in the evening to target/shock level, test FC, test FC in the morning before sun hits the pool. Doing a OCLT is a sure fire way to see if you've got problems other than sun loss of chlorine.

Nip it in the bud.

Using poolcalculator at 10% bleach for your volume with 121 oz only raises FC by 3.4. You're using 8.25. You're not able to keep up.

Jerry Lee · May 23, 2013

Raised FC to 5.5 and will check in the morning to see if I need to shock. Why does it seem to rain every time I try to do this? Thanks!

Jerry Lee · May 24, 2013

OCLT held steady at 5.5 this morning. Tested again tonight and am down to 1 FC which will need 127 oz. of 8.25% to bump back up to a target of 4 FC. When my CYA reagent arrives, I'll test again and try to get my CYA up to around 40 with the dichlor.

spidey07 · May 24, 2013

Jerry Lee said:
OCLT held steady at 5.5 this morning. Tested again tonight and am down to 1 FC which will need 127 oz. of 8.25% to bump back up to a target of 4 FC. When my CYA reagent arrives, I'll test again and try to get my CYA up to around 40 with the dichlor.

Sounds like a plan and it is indeed the sun using up your FC due to low CYA. You can overshoot your target FC by some to compensate for the loss to ensure you never drop below minimum.

You know how to use poolcalculator to see the effect of the dichlor you're adding in terms of FC and CYA? Sounds like you've got a handle on things and have the dichlor on hand you can "get rid of effectively" to reach your goal.

-edit-
nevermind, you're rocking the poolcalculator and understanding the impact

Jerry Lee · May 24, 2013

Thanks again for the input!