FC and light...

[jhieger]

I know it is best to test your water at dusk or is it that you are supposed to treat your water at dusk or later? Here are a couple of questions:

I have the Intex above ground 18' round inflatable ring rubber pool.

Does the FC get eaten by direct sunlight or is it also eaten by indirect light? I ask because around 7:00 pm here there is still plenty of light but no direct sunlight on my pool.

Should I test my water after my filter pump and SWG have done their job so the results show what the SWG added as far as FC goes and then add bleach if it is low? I'd like to run my filter pump, test the water and then treat further if needed. I'd love to do all of that before it gets dark but I want full results so I try to wait until it gets darker so the "light" doesn't cook off any FC at the end of the day. I'd like to start the pump filter and SWG as soon as I can without losing FC the SWG creates and then after that finishes test and treat water if needed. Then test the FC again in the morning to see if it is dropping off by then. I figure if the CC is zero the night before and there is no light that if the is CC in the AM there must be algae. If the CC is zero in the AM the pool is healthy as far as FC goes. Correct?

 

[JasonLion]

It is important that you test at the same time each day, otherwise the results are not comparable. It is best, but not as important, that you test when FC is lowest, which is typically in the early evening, after direct sunlight is off the pool.

FC is lost most quickly when there is direct sunlight on the pool. FC is lost more slowly, but still faster than at night, when there is indirect sunlight on the pool.

 

[Isaac-1]

That is fine the difference between 7 pm and dark is not that big in our region this time of year, chlorine burn off is somewhat proportionate to the intensity of the sunlight, and if you have your CYA in the recommended range you should be fine. If you ever do an overnight chlorine lose test you will probably want to do that twilight to early morning though.

Ike