Which test results to believe?

[lacandelaria]

If your CYA is 140 or higher and CH is 840, a full drain this Fall will be warranted (it's too hot to do it now).

Your FC of 5.2 is about one half of the minimum required for a CYA of 140.
Be aware, the pH test will read falsely high with FC > 10.

You may be able to limp along until mid/late September and the temps cool. But you will have to be diligent with FC and pH. As mentioned, your other option is a no drain water exchange - butchances are to get a 50%-60% reduction in CYA, you will need to exchange close to 75% or more of your pool volume.

Well, that explains the continued high pH readings despite my addition of muriatic acid. (I am testing daily.) We have been reluctant to completely drain the pool because we would like to have some remodeling/refurbishment done and wanted to hold out until then. The pool was installed by the original owner when the house was built in 2006-2007. If you have any recommendations for reputable pool remodelers, that would be welcome. Understand if you would prefer not to stick your neck out on that, however.

 

[proavia]

Well, that explains the continued high pH readings despite my addition of muriatic acid. (I am testing daily.) We have been reluctant to completely drain the pool because we would like to have some remodeling/refurbishment done and wanted to hold out until then. The pool was installed by the original owner when the house was built in 2006-2007. If you have any recommendations for reputable pool remodelers, that would be welcome. Understand if you would prefer not to stick your neck out on that, however.

I am the original owner of my pool, built in 1999. I haven't needed to remodel - yet. My guess is I'm 2-3 years away from that point, maybe more.

Fill water pH usually isn't bad. But we do have high TA, which leads to rising pH. Lowering TA to 60-70 will help reduce the pH rise. But let's look at that after you get a better handle on CYA and FC. For now, just keep pH between 7.2 and 7.6 and the TA will come down some on its own. Don't forget, pH test is not accurate with FC > 10ppm.

Careful chemical management will allow you to get the most life out of your pool surface.
It doesn't take much time, but it does take a commitment and consistency.

Fill out your signature with pool, pool equipment (including manufacturers and model numbers) and test kit info.
This assists us in provide you with help specific to your pool without us needing to ask you each time.

https://www.troublefreepool.com/account/signature

Pictures of the pool and equipment pad also help us get a better picture (pun intended) of what you are working with.

 

[Mdragger88]

I am assuming the reason you say that replacing water lost to evaporation will not reduce the CYA is because the CYA will not evaporate but will simply concentrate in the water that remains? Ergo, the need to drain/exchange. If so, makes sense.

Correct