high CYA, water replacement, and balancing afterwards

dford8583

Active member
Nov 30, 2019
37
Mobile, Alabama
I bought a home with a pool (Approx 21000 gal, chlorine, vinyl liner) and am new to pool care. I want to do the pool myself. I have read a lot on the forum and have read a couple books in preparation. I performed chemical testing on the pool using the tyler technologies k2006c and have my numbers. all my numbers are decent except for the CYA is at 120. I am about to pursue a water replacement operation but had a few questions. I read through the water exchange method in the forum. I think this is the approach I would like to take. it seems like the safest and least involved.
I am interested in developing a step by step approach for this process and figured people in the forum have done this before.

I am wondering after I have replaced enough water to bring my CYA to acceptable levels:
-How long should I let the pool sit after I exchange the water before I test and begin balancing the water and making it right?
-what should be the approach to balancing the water? what order should I tackle things in? chlorine 1st, alkylinty 2, ph 3, etc..?
-Any other pitfalls or things I should be worried about when I do this process? I don't want to screw anything up

Thanks in advance for any input. I hope to begin this process tomorrow so I can have time before the season starts to work out any kinks.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
23,429
Laughlin, NV
Welcome to the forum!
Once you have exchanged the amount of water you wish (I would suggest going at least 10% over theoretical) circulate the pool for a good half day or so. I would add 5 ppm of FC using liquid chlorine during that time. Then run a full set of tests. Get your FC to target level based on the FC/CYA Chart. Then if pH is above 8, adjust to 7.6. Do not worry about TA unless it is below 50 ppm.
I suggest you read ABC's of Pool Water Chemistry.
 

dford8583

Active member
Nov 30, 2019
37
Mobile, Alabama
Did water exchange but my outgoing was higher than my incoming by 5.2 gpm. Drained pool for approx 13 hours it left about a third in the shallow end. I cut the submersible pump off and let my water hoses fill up the pool to acceptable level. After circulating a couple hours, I ran my tests. Got the cya down from ~125 to ~33. I was super pumped. Felt like a consummate pool professional :) my csi # ended up at a 0.2 when i tested. FC=3.2, TA=120, PH=8.2, CH=80. I used pool math app and checked my work in the TT manual. Dosed pool with 13% liquid chlorine and did a 50% dosage of muratic acid with 25%, 15%, and 10% dosages planned for next 3 days with testing in between. I will keep testing and tweaking as I go. I look forward to the continued science project in the back yard lol. Definitely think I am going to ditch the Polaris 280 and go with a robot. Also I still feel like I see particles in the water still.
Wonder if I need to check my sand filter and see if it is out of sand or something.
it has been hovering at 10 psi for 2 weeks. I thought I would have seen a raise in pressure by now.
Any thoughts on the filter?
 

wireform

Silver Supporter
In The Industry
Aug 15, 2017
858
Spring Valley, NY
Well if you know the the gpm of the water source your using it would be easy enough to check the pool fill by how many hours the water was filling. As per numbers calculated, going from 125 to 33 cya is 75% water exchange which is somewhere in the 15,500 gallons area.
 

dford8583

Active member
Nov 30, 2019
37
Mobile, Alabama
Well if you know the the gpm of the water source your using it would be easy enough to check the pool fill by how many hours the water was filling. As per numbers calculated, going from 125 to 33 cya is 75% water exchange which is somewhere in the 15,500 gallons area.
Yes sir, that’s what I did! I just didn’t have a good means to throttle flow on the downstream side to match my upstream flow. I calculated by the time my exchange was done there would be enough level remaining in the pool. I did buy a ball valve for next time so I can pinch back the flow on the downstream side to better match the upstream flow.