What do I add first?

[otter1]

Brand new to TFP! I can see there are several things that need to be adjusted our pool. We previously had our pool maintained by a pool store employee and we were using a floater with the Costco pucks. Once I discovered this site, I tested our CYA and it was phenomenally high. We've since drained the pool a bit to drop the CYA and the new values are as follows:

FC: 3.0
pH: 7.5
TA: 50
CH: 200 or 225 (it was on the cusp)
CYA: 55
TEMP: 55F
CSI: -0.88

We use bleach to chlorinate and have some available in the garage, other things I may need to place an order asap. My question is what do I add and in what order? I know the CYA is still a bit high, but we live in the second sunniest city in the US, so there is significant UV exposure. Also, feel free to talk chem-nerdy to me, I have a biochem degree and formerly worked in a water quality lab, albeit mostly microbiology but some inorganic chem. Thanks!

 

[mknauss]

Welcome to the forum!
Great job on getting a proper test Kit!
Round up that CYA to 60 ppm. The scale is logarithmic so you cannot interpolate between the levels.
What is the CH, TA, and pH of your fill water?
Right now, just keep you FC in the target range based on your CYA using the FC/CYA Levels. You need to add liquid chlorine.
Be aware that most household bleach has additives and is not advisable to be used in pool water. Look for Liquid Chlorine/Shock at Pool stores, Walmart, Home, Depot, etc.
I suggest you read ABC's of Pool Water Chemistry.

 

[Rancho Cost-a-Lotta]

Great first post! Stay away from MA for now. Allow your pH to rise to get CSI into range. Warmer water temps will help CSI also.

 

[otter1]

Thank you for replying!
Chlorine I can do. I use 10% liquid chlorine, no fancy additives.
@mknauss Fill water values: CH 25 TA 40 pH 7.2

 

[mknauss]

Great water. You should have steady pH and TA with minimal CH rise.

 

[otter1]

Other than bringing that FC up, should I add something to raise the TA or the CH?

 

[mknauss]

You could add some baking soda to raise the TA to 70.

Watch your CH. If it drops any you could use Cal Hypo for awhile to chlorinate with. Though, I would think your evaporation will make your CH rise unless you drain off water and replace with your low CH fill water.

 

[otter1]

We don't have plans to drain, but we had to recently because our CYA was 100, thanks to the Costco pool pucks. Prior to draining CH was around 250, I knew it would likely drop CH. I'll try to get my hands on some baking soda. Thank you!

 

[mknauss]

If your fill water CH is 25, and your starting CH was 250 before you drained, then you only drained 20% or less of your pool volume. Does the math add up?

 

[otter1]

Well, it was also raining heavily on fill day, so that may dilute further which is why I wasn't trusting the math directly and instead was relying on the new measurements.

 

[mknauss]

I would have expected your current CH level to be much less. That is what is odd to me.

 

[otter1]

I will run it again, for the sake of science. More data is always fun right?
Pool water x3: 200 each time, fill water: 25

I do see your concern. I will double check my fill water reading when it has been dry. Our source water is surface water (lake) and it has been raining for several days of the last week, so it may be more dilute and not a representative sample test of my fill water for CH. Annual reports for the water district show it around 40, not 25. Of course, we cannot rule out user error on my initial, pre-draining readings, I also didn't use the speed-stir initially. I didn't get multiple data points once I established the CYA was through the roof because I knew draining some was inevitable and that I would have to readjust levels afterwards.