Lowering TA = Increasing CH

[CavVet]

Questions below.
A bit of background: Before I found TFP last summer, i did not know how to test water properly (mainly used strips), i let my CSI get high enough that i had scaling in my pool, to include my SWCG. One day, i had white scale flakes coming out of my jets by the thousands.

Recently, i've been trying to reduce my TA, to keep my CSI slightly negative (which i have not been able to accomplish). In doing so, my CH has been increasing. I have TA creep, due to high TA fill water.
I follow pool math to dose the acid to reduce pH to 7.0-7.2, then i run my water features to increase pH.
FC: 8.5
pH: 7.7
TA: 70
CH: 500 (it was 410 in March)
CYA: 50 (trying to get it to 70)
Salt: 3600
Temp: 84 (ish)
Water is crystal clear.

Questions: should i be concerned that my CH is going up each time i add acid to decrease my TA? Am i causing 'etching'? Should i change my strategy?

 

[Demegrad9]

Muriatic acid shouldn't be increasing CH. You being in Texas are probably seeing high temperatures and a decent amount of evaporation which means a decent amount of make up water. Use your TF-100 kit to test your fill water and post. You probably have a decent amount of calcium in your fill water.

 

[tim5055]

Acid does not raise CH. The CH is coming from your fill water. As water evaporates from your pool only the water leaves (this is like distilling water). Anything in the water stays behind including Calcium and CYA. You add more water from the hose and this "fill water" contains more Calcium. It keeps building up.

Conduct a CH test on the water coming out of your garden hose that you fill the pool from and i think you will find your area has high CH.

 

[CavVet]

Thanks for the replies! I did test my City water, and it is 175 ppm.
I was assuming by lowering my pH I was causing a leaching affect from my plaster. But you both think it is fill water constantly adding CH?

 

[Richard320]

In the summer I gain about 25 ppm per month from evaporation and topoff. That's normal. And CH is manageable up to around 800 ppm when you run out of wiggle room with the pH and TA.

 

[tim5055]

Thanks for the replies! I did test my City water, and it is 175 ppm.
I was assuming by lowering my pH I was causing a leaching affect from my plaster. But you both think it is fill water constantly adding CH?

Yes, it's from your fill water.

 

[CavVet]

Thanks everyone!