Low TA, High CH but SI seems OK

[Mobleycm]

Hi Everyone,
I had a new pool installed about 4-5 months ago. I've been using this forum to keep pool maintained but this is first post. I continue to add about a quart of acid every other day or so to keep PH in check. It will go above 7.8 after about 2-3 days. I've not been too concerned about this as I've read multiple times on this forum this is normal and expected, especially with a new SWG plaster pool. My concern is that although TA has remained on lower end, it has gradually lowered over the last three months from 60 to 40. I think this is due to the acid being continually added. I have not done anything to raise it because I keep my SI in proper range due to my calcium hardness being a bit high. My CH is 550 and has gone up slowly from around 450 to 550 over the last three months. In summary, I have what I believe to be a low TA, high CH but they appear to be cancelling each other out and keeping my SI in ok range. Now that the weather is turning warmer and I just turned the heat pump on, I'm considering whether or not to adjust the TA and CH levels.

Before I take any action, I'm curious if there is any harm to equipment or plaster in maintaining the balance I have right now (Low TA, High CH)?

If it is better to adjust TA and CH to proper levels, I am considering the following plan:
Day 1: Remove 10% of pool water and replace. My city water is TA 190 and CH 230. Hoping this gets CH to 350-450.
Day 2: Raise TA using sodium bicarbonate to get to 70. The water replacement from Day 1 will raise TA as well so will be curious how much more I have to adjust, if any.
Day 3: Adjust PH back to proper range.

My current measurements are:
Water temp: 73F and rising with heat pump running
Ph: 7.5
FC: 1.8ppm (I turned up the SWG yesterday to raise to 3-4ppm)
TA: 40
CH: 550
CYA: 40
Borates: 40

Thanks in advance for any advice you have for me.

Regards,
Chris

 

[kimkats]

HI! I can tell you have been reading quite a bit! NICE!

I am going to touch on the CH........please get your paperwork for your heater. I have read that some heater require a CH of ?? If your heater's warranty says that then..............Please let me know what you find out. I want to learn along with you.

Kim

 

[duraleigh]

I do not use CSI. Keeping your parameters withing the guidelines we suggest for TA, pH and CH will negate the need for CSI in almost every case.

So, my suggestion for your pool is to lowr pH to about 7.5 with muriatic......then bring the TA up with baking soda to about 60-70........leave CH alone for now but monitor and drain and do a partial drain and refill when the CH goes over 600 (of course, that may not be too long)

Alternatively, you could drain and refill about 20% of your pool water which would solve your TA and pH issues and reduce your CH a little (475).

You have a very good grasp of your chemistry.......chose what you want to do.

Obviously, the goal is to reduce the chance of scale. Keeping your pH in the 7's and keeping your CH manageable are the key components to that.

 

[bobodaclown]

Hi Chris,
You're doing fine. I'd keep testing and watching the numbers. Borates help with buffering Ph swing, having a low TA helps counter the high CH. I was in a similar situation. My CH has slowly come down due to rain water filling pool. You'll want to bump your CYA up to around 70, and that will bring down the Ph, aerate to bring the Ph up if needed. I wouldn't necessarily chase numbers if the CSI is good, you have enough residual FC, and the water looks good.

 

[Mobleycm]

Kim,
Thanks for the quick response. I just broke out the heat pump documentation. The owners manual (including warranty terms) are only 12 pages and there is no mention of requirement of CH levels. There is only a general statement to check water chemistry regularly and that warranties may be void for damages as a result of poor water quality.

Thanks,
Chris

 

[Mobleycm]

Dave & Bobodaclown -
Wow, I wasn't expecting such a quick response. After reading your responses, I'll monitor the CH, get the CYA back up to 70 and will go ahead and adjust the TA to get at least to 60. I have been diligent with maintaining the pH so if I keep at 7.5, and raise the TA to 60-70 then still in good shape even if CH approaches 600. I've been using the rain as well to lower the CH so would be nice to avoid partial drain/refill. Thanks!!!! This forum is fantastic!