Flow rates and chemicals throughout the day. ...

isriam

Well-known member
Jan 15, 2015
201
PHX
One thing that bothers me is how people run their pumps 4 to 8 hours a day and at night only. But I don't follow how chlorine loss during the day could survive without turn over? If you run only at night your water is stagnant all day and wouldn't the top few feet have fc0? And if you run it during the day what time do you add bleach? If you add it in the morning you run a chance you have fc0 over night and if you add it in the evening then you are kinda forced to run your pump over night?
 
The key is understanding your pool's chlorine usage and adding enough chlorine to keep FC above target until the next time you test and add.

If CYA is 40
3 is the minimum FC and should never ever get down to 3
5 is target to keep it at or above
16 is shock level

So, it is safe to swim when FC is between 3 and 16.

The pool needs to have 5ppm at the end of the day, early evening, since that is usually when it is lowest. If your pool normally uses 4 ppm of chlorine and you want to add in the evening then test and take it to 9 ppm. That should have it be at 5 ppm the next time.
 
So if I have 50 cya I should check after dark and record my usage so I can guess how much to add each evening to cover the next days sunshine?

So if I drop 8fc then I can add enough every day to cover that and keep it near my max fc? Also does that mean it's best to run your pump during the day? I used to run my pump only at night before I understood tfp and lights affect on chlorine.
 
Test your FC a couple of times per day and write it down for a week and you will see a pattern. You can run the pump any time you want. A lot of people want to run it at night because their electric rates are lower. Or you can split it and run a few hours at night and a few hours during the day to split up the skimming.
 
Ok so does flow rate and turnover affect fc and chlorine loss via light? I know turnover is a fake standard that doesn't matter but I thought water at the surface lost chlorine faster than at the bottom.
 
You are correct, pool turnover is not a factor with residential pools. I am not aware of surface water losing chlorine faster than deeper water, I believe that chlorine stays mixed in water and does not stratify. You could try an experiment and run the pump one day and not the next starting with the same FC to see if you lose more with or without the pump running.
 
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