Makes sense however We really haven't been in the pool all that much due to the cooler temps at any rate I will gear up for a slam and re-test after the sun goes down this evening. I do use Trichlor tabs in my auto chlorinator so I do watch the CYA constantly. I have also had to drain quite a bit of water due to rains. Oh and I do use my solar cover regularly when we are not using it.Depends when you test and when you add. Test in the early evening to see where you are. if you are at 4ppm at noon and everyone goes swimming then you will be below minimum FC level by the end of the day. I'm an aim for the high side of the range kind of guy. A little extra chlorine in the pool is not going to hurt anyone. I swam all weekend with chlorine well above 20ppm and CYA of 70 because I have some algae spots myself that needed some work because of too much swimming and not enough testing. My FC was 1.5ppm Saturday morning and then I spotted a few algae spots.
So, CYA of 40
minimum 3, target 5, shock 16
Means it is safe to swim when the chlorine is between 3 and 16.
Target is 5 because most pools lose about 2ppm of chlorine per day. But, if you have several people swim for 6 hours then you are going to lose more than 2ppm. Minimum level of 3 means that the level should never, ever drop below 3 ever.
I would target FC at 6 or 7 at all times and if you know there will be lots of swimming take it up to 8-10 before swimming, test after to see where you are and take it up to 8-10 again.
I was not aware of that. My pump is on a timer and runs 3 times daily on low speed. Where should I point the return? Towards the surface or the bottom? I do have a "robot" but have had less that favorable results since it will not run on low speed very well.Looking at your picture of the pool made me think that you have a problem with the water circulation. It is possible that you have low chlorine concentration on the lower part of the pool if water is not well mixed up. I see that you have a robot. Put it to work. It will mix the water layers and bring the chlorine closer to the pool surface where is needed. Without a good chlorine distribution it is possible to have low chlorine concentration closer to the bottom of the pool if there is a temperature gradient and the water is not well mixed up.
I am late to this dance but want to comment on this very common misinterpretation of what we see in our pools.Short of the stuff on the bottom the water is clear.