Please review my test results and tell me what you think...

[Denise O]

Greetings,

Pool test results:
Total chlorine: 8.5
PH 7.7
TA 40
CYA 80 (Still working on lowering it with rainwater- down from 140 so far but no rain since January here in Nor Cal.)
CH 300

Did all my testing, then took water to pool supply since I was picking up liquid chlorine.
They found my TA to be 67 and recommended 18.5 lbs of their expensive "baking soda" product @ $32 for 10 lbs.
I bought some baking soda @ $1 lb and continued my research on dealing with this here with you folks.
I put my numbers in the pool calculator and it said to add 8 lbs of baking soda. I've never dealt with TA, so I'll start with the 8 lbs and retest the water.

My water temperature is 50-52 degrees. Any advice on these test results?

Also, I'm using cartridge filters. When is the best time to clean the filter? The pressure gauge hasn't gone up and frankly I don't swim, I just like to look at the pool, so there isn't any swimmer's products in the water. Lastly, I don't have a cover but don't have trees in my yard that blow into the pool.

 

[mknauss]

What is your fill water TA? Odd to have low TA in the west.

 

[Denise O]

I turned off the auto-fill in December, so the only new water is rain water. So, you want me to check the tap water?
I'll get right back to you...

 

[Denise O]

Tap water TA is 110.... Any idea what the TA is on rainwater? I drained as much as I could before each heavy rain and let it fill the pool. We're only talking maybe 3 inches at a time....

 

[mknauss]

OK -- so be careful adding baking soda. When spring/summer arrives and you start to use that tap water for fill water due to evaporation, your TA and pH will rise. You will be adding acid.

To be honest, with a pH of 7.7, I would suggest you not add any baking soda. Just monitor.

 

[Denise O]

Ok, I'm happy to monitor. I'm probably going to add tap water soon because I've had 2-3 inches of evaporation while waiting for our next rain.
The pool store's low TA warning of equipment corrosion and surface damage made me think I needed to act quickly in adding the baking soda.

Given my current results, how low can I let the TA go (assuming it goes lower before I add water) before I need to worry?

Thank you!

 

[mknauss]

TA by itself is not an issue, it is combining the pH, TA, CH and water temperature to get what is called Calcium Saturation Index (CSI)
Your CSI right now is negative. So it would be best to get your TA to 50+ soon. But adding tap water will do that. And the pH at 7.7 helps balance the TA.

If the TA goes to 30, add 30 ppm TA worth of baking soda.

 

[Denise O]

Understood - thank you.

 

[Cena_sea]

I recently had to add baking soda to raise a TA of 40 too. I added enough to raise to 50. Then added more baking soda to get to 60 but it took several days to register the increase. My TA is lowering due to muriatic acid. Still I'd like to keep the TA on the lower end because I have high ph. Also for me calcium numbers have gone down over the last few months naturally to about 375, but it sounds like 300 is okay too. I did test the fill water for ch and mine was slightly blue after 1 drop but really blue after 2 so I think its 50. Next time I run tests I need to test the TA fill.