General chemistry and tile scale question

[Gingermom]

I have a 15,600 gal in ground pool built @ 2007. It does have a spa and heater. There is some calcium scale along the water line. Before I work on removing it, I want to make sure I understand how to keep it from coming back.
Current stats
CL -5
pH 7.4 ( I have to regularly add acid to keep it in this range - so not sure if that is indicative of some other problem)
Alkalinity - 90
CH - 350
CYA - 180

The pool store wants me to drain and refill half my pool and raise the pH.
Using the Pool Math App, it seems like if I keep the pH in this range the higher CYA is okay - As the water warms up into the 80s and 90's I would need to lower the pH for things to stay in sync? Am I understanding that correctly? Does that have any negative impact? Should I replace some of the water to lower the CYA?

What is the ideal CSI to keep scale from forming? Do any of the descalers work or is elbow grease and 25% acid the best option for the DIY? If it's polished ceramic tile what type of scrub pad (I don't think pumice stone is hard enough from what I have read, and then you get all that pumics dust on the bottom) can you use? Scotch-brite makes several levels.

 

[pjt]

How are you testing? How are you chlorinating?

If your CYA is really 180 (measured yourself with a quality test kit), you'll need a partial drain and refill. That is your biggest problem right now. Once you've done that, maintain proper FC for your CYA level. FC / CYA Chart

Keep your CSI slightly negative to avoid calcium buildup. Use PoolMath for your calculations.

Stop getting chemistry advice from a pool store!

 

[Gingermom]

How are you testing? How are you chlorinating?

If your CYA is really 180 (measured yourself with a quality test kit), you'll need a partial drain and refill. That is your biggest problem right now. Once you've done that, maintain proper FC for your CYA level. FC / CYA Chart

Keep your CSI slightly negative to avoid calcium buildup. Use PoolMath for your calculations.

Stop getting chemistry advice from a pool store!

Yes tested everything with a "real kit". May not be exactly 180. The dot disappeared before it reached any reading, so I used half pool water half tap, and multiplied the result by 2. How low do I need to get the CYA...aka how much water will I need to replace.

 

[mknauss]

Could you please add what kit you use to your signature?

As you live in Houston, draining a pool entails significant risk. You should consider doing an Exchange. You will want to exchange your entire pool volume as it is not 100% efficient. Your goal would be a CYA of 40 or 50 ppm.

Draining - Further Reading

www.troublefreepool.com

 

[YippeeSkippy]

Please add to your signature line how you chlorinate your pool?

You can drop your TA a bit to help manage your pH rises.

Lower Total Alkalinity

A lower Total Alkalinity level can help a pool owner stabalize their pH increase. We'll explain how to lower TA with a little help from muriatic acid.

www.troublefreepool.com

350ppm of CH is a good place to be for your pool. So pay attention to your CSI if you're having problems. Using PoolMath you can see how tweaking different items at times alter the CSI. I personally prefer the old classic web version of PoolMath (found below on website) easier to show how tweaking things help/hurt your CSI.

Maddie