New pool owner. Cya level over 100. No free chlorine detected....help

[Watermom]

Gotcha. I didn't realize that your CYA reading was from dilution. The fact that they got an FC reading of 5+ shows that your kit is better than whatever they are testing with. 5+ on a test kit that only goes to 5 means that it could be 5 or any number higher than that.

When you post your numbers tomorrow, post FC and CC in addition to pH and TA. No need to run the CYA test again.

[LisaBP]

Thank you. Here is what I got yesterday:

FC: 8
CC: .5
PH 7.4
Ch 270

This chlorine ratio seems out of balance. What do you recommend?

[Watermom]

What is your TA reading? How does your water look?

You are at the minimum chlorine level for your CYA. Take a look at this chart for more about the relationship between CYA and needed chlorine levels: http://pool9.net/cl-cya/ Go ahead and add some bleach now so your chlorine doesn't dip any lower through the day.

[PoolDoc]

Her TA was 180 a few days ago.

Composite:

TA = 180
CH = 270
CYA = 160

Given a CYA=160, as long as your pool is algae free, you need to keep your FC between 8 and 16 ppm. Don't worry about CC, so long as it's only 1 drop of FAS (0.5 ppm with the 10 ml sample size).

So, to respond to your question, your chlorine is fine, except a bit low.

Given your high TA & moderate CH, you need to lower your TA a bit. If you would lower the pH to 7.4 or so, and retest TA to confirm. To lower, see http://pool9.net/ma/

I looked at your data, and recalculated your volume as 6,300 based on the dimensions you provided. If the depth measurements were pool depth, rather than water depth, the actual volume is even less.

[LisaBP]

Thank you, PoolDoc. I didn't see this reply before posting mine. I will lower the ph. There is not and hasn't ever been any algae as far as I know. The pool is approx 8000 gal according to my pool service company. I did not measure the depth and length, I just estimated. I will get an actual measurement and update it.

It doesn't sound like you are concerned about my high cya number. I understand that having a high cya means keeping lots of chlorine in the pool. I'd like to have my pool water be as healthy as possible for my kids to swim in. Wouldn't using less chlorine achieve that? What do you recommend? Thank you.

[Watermom]

It is up to you. You can do a partial drain and refill if you want but don't totally drain it. OR, just keep the CYA at 60 and run the higher chlorine levels per the chart. It is fine to do so and your kids can certainly swim with no problems.

[PoolDoc]

CYA and chlorine combine in such a way that, the higher the CYA, the less % of the chlorine that is active. In a very important sense, in a pool with 1 ppm FC at CYA=20 ppm there is the same amount of ACTIVE chlorine as another pool with 5 ppm FC and CYA=100 ppm!

The studies of health risks possibly originating from chlorine in pools, are studies of INDOOR COMMERCIAL pools. Compared to outdoor pools, indoor pools have very poor ventilation. Commercial pools have MUCH higher swimmer loads then home pools. And, perhaps most important, indoor pools don't have the high energy oxidation processes that occur when solar UV photolyses pool chlorine. This process rapidly break down the noxious chlorine + people goo compounds which form, as chlorine tries to clean up the mess people leave behind!

As far as I can find, there is NO data suggesting that swimming in OUTDOOR pools with FC=20, or even 50 ppm. In fact, dermatologists have for years been treating various sensitive skin conditions, in both adults and children, with "bleach baths" where the chlorine level is 50+ ppm, and there is NOT stabilizer.

All that to say, your kids will be fine, as W-M has already told you!

[LisaBP]

Thank you, Watermom. So I added another gallon of Walmart 8% bleach early this morning and my pool service added some acid last week.

Here are my numbers:
FC 11.5
CC .5
Ph 8+
TA 160
CH 52

I looked at the best guess chart but don't understand. For my high cya number, should I be aiming for FC of 8 to 15? What does the shock column mean? I need to have my pool swimable by the weekend. Would you advise me to drain some of the water?

Thank you so much.