Pool loses a lot of chlorine over night but little during the day

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J

jkl1

0
Jun 27, 2015
7
Fair Lawn, NJ
Hello everyone, I am facing a weird situation with my 20,000 Gal inground pool since opening over three weeks ago. The pool had CYA 0 right after opening and all the chlorine in 4lbs of trichlor shock was eaten up in less than two hours. The water has been crystal clear right after opening. After two more trichlor shocks I switched to shocking with 8.25% household bleach and the chlorine loss is now less dramatic. However, after three weeks of keeping the pool at shock level plus intermittent brushing we have somewhat reached a steady state with little loss over the day, but some loss over night. CYA is 50 with a shock level of 17, and the loss is from 19.5 to 15 over night (typical for the previous light), but at day in sunlight the loss is only around 0.5-1. Combined chlorine is about 0.5. I am running out of ideas what to do, apart from continuing this through the rest of the season with this abnormal use of bleach.

I appreciate any ideas from the experts here.
 
Hey! You haven't completed the SLAM Pool School - SLAM - Shock Level And Maintain process until you pass the overnight chlorine loss test (OCLT), which you have not yet. Are you sure that it is not more of a time factor and not a sunlight factor as to why the chlorine loss is more at night? Most people test more during the day, especially during a SLAM than they would at night, hence a greater CL loss at night.
 
Loosing FC overnight means that there is something organic in your pool is using the FC. What times are you testing to determine this loss? Are you taking the reading after dark and then again before sun is on the pool?

SLAM level for CYA=50 is 20ppm. Have you been keeping FC above 20ppm through the SLAM? Are you using bleach only to add FC?
 
Thanks, perhaps this was my mistake. Poolcalculator.com says that the shock level for CYA 50 is 16 and not 20. Yes, I am only using household bleach (8.25%).

Let me to keep the shock level above 20 for a couple of days and then get back here if nothing has changed.
 
Please use PoolMath. The link is at the top of this page. The poolcalculator you stated is not supported.

Take care.
 
Thanks again for all your help. Unfortunately, the pool still does not hold chlorine. I have maintained the pool well above shock level over 20 ppm almost permanently over the last four days (CYA 50). The pool looses roughly 4-6ppm every night (measured between 9pm and 6am, yesterday from 31 to 26 this morning). I also rechecked my CYA several times and maintained the pH at 7.5. I am running out of ideas what to do. Would partially draining and refilling the pool help? Is there anything I may have overlooked? Any advice from the experts here is highly appreciated.
 
Have you checked behind any lights you have? What about looking REAL close at the skimmer face and door?

You do not have your signature filled out so I am not sure what kind of steps you have. If it is an above ground pool the steps could be a problem.

I also have to ask if you have kids.........teenage kids at that............are they swimming at night?? It has happened before so I have to ask.

Kim:kim:
 
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