High CH, high CYA, low T/A....questions...

[AB]

Hello,
I have been taking the pool chemistry readings with the TF-100 for about 9 months now...my most recent readings are:

T/A: 60
CH: 400
CYA: 105

Back in August they were:
T/A 120
CH: 390
CYA: 50

Is this something I need to worry about? I see some varying ranges for 'ok' readings...but based on the pool calculator's target numbers (default), it says I need to add 81 oz baking soda to get the T/A back to 100,
And replace 35% of the water to get the CH back to 260, replace 62% of the water to get the CYA down to 40. It sounds like some drastic changes are in order....

Wanted to get a second opinion as draining 2/3 the pool would be quite expensive...(also does new water have a CH of 0? how can you tell?)

Thanks, Aaron

 

[duraleigh]

Reduce your CYA. Down to about 40-50 if you are manually chlorinating and around 60-80 if you have an SWG.

Your CH is high but fairly manageable. It will be a bonus that it will come down when you take care of the more important issue of CYA.

What is your pH? How does your water look?

 

[AB]

Hi, am manually chlorinating.
Ph is around 7.4.
Water looks ok , clear, but a little "yellow dust" at some places at the bottom of the pool. Guess it is algae.

Are there other ways to reduce CYA besides draining the pool?

Thanks!

 

[chem geek]

If you are manually chlorinating, then how did your CYA rise over time? CYA would only increase from using Trichlor pucks/tabs (or granular) or Dichlor granular/powder or adding pure CYA. Also, how do you get a reading of 105 for the CYA level? The test kit would only let you estimate perhaps 100 or 100+ -- did the dot disappear with the level slightly below the 100 line?

As for the TA, you don't need to go above 80 ppm as you have a reasonably high CH level though this partly depends on your pH level. If you don't have a problem with the pH rising over time, then a TA of 100 ppm would be OK, but usually that level tends to make the pH rise faster.

Fill water does not have zero CH, though it does have zero CYA. For Raleigh, North Carolina, the October water quality report gives an average year-to-date TA of 34.2 and a Total Hardness of 31.5. The Calcium Hardness (CH) will be less than the Total Hardness, usually around 70% so around 22 ppm in your case. Basically, your fill water is low in CH so will need more calcium chloride added to it after any water dilution of your pool.

 

[AB]

Hi chem geek,
I am using Trichlor pucks...Sorry, I misunderstood when the first person asked if I was using a SWG. I just meant I did not have an SWG and was 'manually' chlorinating myself.
You are also right about the 105 reading it is an estimate of the dot disappearing, slightly below 100.

So I guess I need to replace some water to reduce the CYA, then add the calcium chloride to reduce the CH?
Thank you!

 

[duraleigh]

then add the calcium chloride to reduce the CH?

No, that will increase your CH. Assuming your fill water has less CH than your pool, the CH and CYA will both come down when you do a partial drain.