Chemistry Question re: High TA

[birkesl]

I have the following readings 4 weeks into startup with addition of high iron hard well water on a weekly basis. Can anyone help me understand if TA is high what I should do differently and if that even matters?
CC-.5
FC-2
TA-180 (rose from start of 100)
CYA-10
PH-7.6

 

[JVTrain]

You're having to add water on a weekly basis? If so, have you done the "bucket test" to see if you have a leak?

If your TA is rising, it has to be coming from an external source, such as your fill water or chemicals. Test your fill water for pH, TA and CH and post those results.

 

[JoyfulNoise]

Can you test your well water for pH, TA and CH? Do you know how much iron is in your well water?

TA only increases for two reasons, your well water has high TA and/or you're adding TA from either baking soda or soda ash. Are you adding TA?

 

[birkesl]

Well water is pH 7.2 and TA 360 so very high yes. Does TA really matter?

 

[JoyfulNoise]

Well water is pH 7.2 and TA 360 so very high yes. Does TA really matter?

Yes, it absolutely matters at that level. High TA is the primary contributor to constant pH rise. Your acid demand will be high because of it.

People who have high TA fill water need to limit evaporation as much as possible. Use of a pool cover is highly recommended. There is an article in Pool School on how to lower TA.

 

[Donldson]

Yes, it absolutely matters at that level. High TA is the primary contributor to constant pH rise. Your acid demand will be high because of it.

People who have high TA fill water need to limit evaporation as much as possible. Use of a pool cover is highly recommended. There is an article in Pool School on how to lower TA.

I will point out that it is less of a concern here in the Midwest than it would be in your neck of the woods since through a large portion of the season we get plenty of rain to keep us topped off. I usually go through 3-4 gallons of MA in the first month of the season and then only 1 more over the rest of the season as I only need to top off a couple of times during the heat of mid Summer.

 

[JoyfulNoise]

I will point out that it is less of a concern here in the Midwest than it would be in your neck of the woods since through a large portion of the season we get plenty of rain to keep us topped off. I usually go through 3-4 gallons of MA in the first month of the season and then only 1 more over the rest of the season as I only need to top off a couple of times during the heat of mid Summer.

That makes sense. By comparison my fill water has low TA (~100ppm or so) but my evaporation rates are a lot higher (100" annually on average). I barely go through 4 gallons of MA over an entire summer (Jun-Aug). So that's a great comparison of how high TA affects acid demand.

 

[Donldson]

Yep, for comparison we get about 45" evaporation annually and average 3-4 inches of rainfall per month over the summer, so much more even here. My big TA influx is in the Spring since I drain about 1/3 of my pool to close, leading to over 5000 gallons of 400+ TA fill water. I started with 200 TA this season and it would rise so quickly that I could dose with acid twice a day. It is finally down to 120 and although I am adding acid daily it is much less.

So to birkesl, yes it is important to mind your TA but as long as you are testing and adjusting your pH daily then it will fall to a more reasonable level. You are just always going to want to keep acid on hand. I can't even recall a time where I have had to raise my pH or TA since switching to liquid chlorine.