High chlorine demand

Chlorinating, maintaining the right chlorine levels,
chlorine problems. Dichlor, trichlor, cal hypo, bleach,
granules, chlorine pucks and chlorine sticks.
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Joined: Mon 19 Jul, 2021 20:01
My Pool: Ingound 10,000 gallon
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Pentair pump
Sand filter

High chlorine demand

Postby Shinebsr » Mon 19 Jul, 2021 20:21

Hi everyone, I’m hoping I can get some advice as to whether or not I’m on the right track.

This year we have had relentless rain in western NY and I battled with a mustard algae problem when opening my safety covered 10,000 gallon inground pool. I got things back to normal after 15 gallons of chlorox. All my chemicals have been balanced as follows:

Cya: 60 ppm
Alkalinity: 110 ppm
Calcium: 250 ppm
pH: 7.4
Chlorine: 0.5-1 ppm

The chlorine level is what has me stumped. I will use 73% cal hypo when needed (usually once a week), otherwise I am using 2 3” trichlor tablets weekly, 1lb non-chlorine oxidizer, pool perfect, polyquat 60, and the occasional splash of bleach.

When I saw pink algae two weeks ago, I knew there was a problem even though the pool is crystal clear. I measured the chlorine today and it was 1ppm TC with 0.8ppm CC and 0.2ppm FC. With my stabilizer level and pH I calculated I need around 7.5ppm chlorine. So I decided to superchlorinate… I dumped in 2 gallons of bleach (around 20ppm chlorine) and it was gone in 45 minutes (back to around 2ppm). I added another 2 and it dropped to around 3 ppm after another 20 minutes. I added a fifth gallon and it dropped to around 4 ppm after around 20 minutes.

I’m not sure if it’s the stabilizer sucking up the chlorine or organics so I added 2lbs of oxone. I realize the combined chlorine will now be off but the FC is just not staying above 4ppm.

I know trichlor pucks is the first thing to go so I stopped those. I’m just wondering if this is a pink algae problem that isn’t totally visible other than a couple streaks on the ladder and a pink filter sock, or a stabilizer problem. I backwash maybe once a week but not less than once every 2 weeks. Should I be adding liquid bleach daily to get to the 7.5ppm, or will the cya bound chlorine get released as needed and I only need to add chlorine every few days? Do ai keep adding liquid bleach until I get to 7.5 for some period of time?

Thanks in advance for any solutions!


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Re: High chlorine demand

Postby Denniswiseman » Thu 29 Jul, 2021 09:00

I seem to have missed this
Forget about 7.5 With a CYA of 60 you need a Slam level of 24 to do any good
Slam (Shock Level and Maintain) with relation to Chlorine / CYA Chart and Recommended Pool Levels

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