High Bleach Requirements.

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GypsmJim

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Aug 1, 2015
74
Wheatfield, NY
Have had a pool for 28 years. Struggled along for awhile and then found this site. Bought a TFT test kit and our pool has been PERFECT for 5 years now.

Opened the pool 2 weeks ago. The water was crystal clear and virtually no dirt (a new cover last fall).

Tested ALL of the parameters and everything was within the Pool School specs. (BELIEVE ME WHEN I SAY THAT SO DON"T ASK WHAT YADA YADA WAS)

Added some CL after a few days (as necessary) to maintain the required free CL. Still maintaining as required, no problem.

My issue is that in past years my daily requirement was 1.5 quarts of bleach, and this year I need to add 4 quarts every day in order to maintain.

The CYA is 40 (in specs) and it has been the same every year at startup. I am using Sodium Hypochlorite (concentrated) from a local chemical company. Its the same stuff I have used for 5 years now.

The weather is "normal"....not unusual temps or rainfall.

My question is what could cause the high bleach requirement?
 
It was unseasonably HOT yesterday in NY.... I came out of La Guardia and it was hotter than the Georgia heat I left by 10 degrees, so I'm not totally surprised you're using more liquid chlorine than normal.

Maddie :flower:
 
Hey Jim !!! Anytime, ever, that you suspect something funky, perform an Overnight Chlorine Loss Test to rule out algae. It can sit right on the edge of being visible and your frequent testing is the first line of defense to catch it before it becomes pea soup.

People don’t like hearing this because they think it means they were at fault. ‘But my water is PERFECT blah blah blah’. Many times they aren’t at fault at all and it happens to the best of us.

Once you rule out algae we can go after other things like bumping your CYA to see if the pool responds better, but the KEY is that there will be no worries if it takes a bit to figure out.
 
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As the others here have mentioned there can be other contributing factors at work here. The CL is either being consumed as it sanitizes the pool (something in the water not readily apparent), lost (increase in sunlight or higher aeration), or your CL supply is suspect (bad lot, stored poorly, etc).

I'd start looking where cj133 stated... see what level your FC rises to shortly after addition. If it doesn't rise to the calculated levels, then your CL supply is suspect. If the levels do increase to the calculated levels, then monitor your overnight Chlorine loss as others mentioned.
A solar cover and ensuring you're not getting high aeration (from line leak or return aimed at water surface) can help eliminate the potential of the CL being lost to those issues.

If that's the case then you're looking at an unseen contaminant chewing-up your CL and you may need to SLAM for a bit to get things back to your "normal' CL usage.

Best of luck with the issue. Hopefully it's remedied soon.
Respectfully,
 
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Yep, I would dose to get to a certain level and test shortly after. That will tell you if your chlorine is as strong as you believe. Also, is your water at the same level?
 
I'm not in La Guardia, I'm at the other end of the state. It's been warm, but not unusually so.

It's fresh CL, not last year's. 4 qts seems to bring it to the same level as 1.5 in the past.

The overnight FC drop was 1.0, but the pool did have sunlight on it for a couple hours before I tested it.

We'll soon go on vacation and I'll switch to the automatic chlorinator that uses slow dissolving pucks. That will bring up the CYA so we'll see what happens.

Thanks for all the comments...
 

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GypsmJim said:
I'm not in La Guardia, I'm at the other end of the state. It's been warm, but not unusually so.

It's fresh CL, not last year's. 4 qts seems to bring it to the same level as 1.5 in the past.

The overnight FC drop was 1.0, but the pool did have sunlight on it for a couple hours before I tested it.

We'll soon go on vacation and I'll switch to the automatic chlorinator that uses slow dissolving pucks. That will bring up the CYA so we'll see what happens.

Thanks for all the comments...
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Did you test ~30 mins after CL addition to see if the effect matches poolmath? Or is the 4 gals equals 1.5 gals you mention after many hours?
 
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GypsmJim said:
Yes, it was tested and it DOES match the pool math. My question was "Why?". So, OK, the bleach is doing what it is supposed to do. I admit I didn't do the math last year, I simply added 1.5 every day and all was well.
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So, you don’t really know if the 1.5 last year brought you to the same level as 4 quarts this year. And you’ve told us not to ask about your actual test results. You also have not shared what FC number you are actually targeting.

Your signature says that your pool is 13,555 gallons, and that you are using 8.25 % bleach. You’ve stated that your CYA is 40.

Using Pool Math for a vinyl pool of your size at that CYA and that strength bleach, it tells me to add 100 ounces, or 3 quarts and 1 cup, to get to target of 5 FC.

1.5 quarts of 8.25% in a 13,555 gallon pool would raise FC less than 3 ppm. If you were only doing that every other day last year, you got lucky.
 
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All my test results are mid range of what this site says they should be. I was just trying to save time and not have to type in all those numbers. (I'm just lazy)

My FC target is 5, which is what you guys say it should be for 40 CYA. It was running only 1.5-2.0 every evening and that's why I had to go to 4 qts.

I added 1.5 EVERY day last year. I thought I said daily usage, not every other day.
 
GypsmJim said:
All my test results are mid range of what this site says they should be. I was just trying to save time and not have to type in all those numbers. (I'm just lazy)

My FC target is 5, which is what you guys say it should be for 40 CYA. It was running only 1.5-2.0 every evening and that's why I had to go to 4 qts.

I added 1.5 EVERY day last year. I thought I said daily usage, not every other day.
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Good info - if you're seeing FC of 1.5-2.0 with CYA40 at the end of the day, you're in the danger zone for algae.
I can tell you from personal experience that algae starts and the pool still looks great. But it's there and it's able to take a lot of FC with it!
 
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