Combined Chlorine

[dmccarthy]

Just opened my pool about a week ago in Massachusetts. It's a SWG and the pool company opened. The water was pretty clear and blue (other than some debris on the bottom) after the safety cover came off and they did the standard adding about 5 gallons of liquid chlorine and some algaecide. The water temp was around 60 degrees when they opened so I started testing all the chemicals immediately after. I have the recommended taylor test kit so I am able to test the chlorine at high levels with accuracy.

When I first tested the FC levels were around 18 and I was getting around 40 or so for CYA levels (so I thought the SLAM numbers were hight enough based on the SLAM/CYA chart), but the pool temperature was only 60 degrees and I thought I have read that CYA levels are not accurate below 70 degrees and could actually read artificially higher. I did NOT add any additional chlorine, I did brush the walls, and I did perform a few OCLT's (I kept my SWG off during this time) and the loss was less than 1ppm overnight and the water has been clear throughout. So I was confident that things were going well and I have slowly let my my FC levels drop over the last several days until I got to about 5 and I have now just started turning on the SWG to maintain. I also was going to wait until the water temp increased before testing the CYA levels. The CYA was about 70 at the end of the season last year before I closed.

My pool is right at 70 degrees now and my CYA reading last night was about 65 or so (it jumped up since my initial reading). The only thing different is it rained really hard the other night and when I tested the chlorine levels the FC was around 6, but I now have some CC around .5ppm (which I previously did not) and wonder if I should SLAM again? I am just a little confused as I was passing the OCLT but now have CC where I previously was not. Is that normal after rainfall or is this just the byproducts of all the initial SLAM? Do I need to get my FC levels back up to SLAM levels to address? I recognize my CYA tests may not be totally accurate right now so I am reluctant to add stabilizer until the water temp increases and that my FC is a bit high as well, but nobody is swimming in it yet anyway. Again, the water has been very clear throughout. Any help or suggestions on what to do would be most appreciated. I am still a bit confused as to how to correctly address CC and which is the best method.

These were all the levels last night:
Temp = 70 degrees
FC = 6
TC = 6.5
pH = 7.5
TA = 110
CH = 180
CYA = 60-65ish

 

[Texas Splash]

A CC of 0.5 is still treated as zero here, so you are okay. But continue to watch it. It may be fluctuating as it processes heavier amounts of organics that are waiting to be burned-off by the sun..... organics from your rain/storm, or by-products from chemicals added during opening. Now that you have a higher CYA, watch the FC to ensure it stays on the higher end of your target. When in doubt, run another OCLT with the SWG off and it will confirm if you have algae or not. Have a nice day.

 

[cowboycasey]

Your CYA will read fine but you are correct, I heated my water in the microwave to about 75 degrees and measure it, worked great as you know with a SWG pool your need CYA at 70 or 80..

Your FC level dropping and your CC going up is normal because you're fighting something (could have been from the rain dropping stuff in the pool) but probably not enough for a SLAM, but there is no issues with taking your FC to slam level now

adding CYA
letting your FC drift down
adjust your SWG to keep your FC around 6

your doing great and following the most important part of TFP, knowing what your pool is doing

 

[dmccarthy]

Will do, thanks very much.

 

[dmccarthy]

much appreciated, thanks for the responses and for the explanations. Think I understand it a lot better.