Hello! I am opening our pool for the year and every year I feel like I have to relearn and remember how to do everything! My question is that I put 1 gallon 10% bleach in (30,000 gallon gunite pool) each day the last 2 days after opening and my free chlorine is barely registering the day after. Is this normal on opening after the winter? My water chemistry other than that is within normal ranges. Combined chlorine is showing slightly, like 0.5. Should I SLAM or should I just wait it out as there is still some leaves and debris that I have been in the process of removing. (Most of it is almost completely out now). The water is clear for the most part but I can tell it isn’t crystal clear yet. Thank you!
Opening pool and chlorine demand
- Thread starter harrysmary
- Start date
- May 11, 2021
- 973
- Pool Size
- 7000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-30
What is your CYA at? What do you mean by barely registering?
1 gallon 10% bleach in (30,000 gallon pool is about 3.3ppm chlorine...
1 gallon 10% bleach in (30,000 gallon pool is about 3.3ppm chlorine...
Adding that much bleach with your pool volume add 3.3 ppm of FC. Depending on your CYA, it's not unreasonable to have that used up in a day.
Sorry I forgot to mention CYA is low (below 30). My kit only measures starting at 30 so I’m not sure exact number. I always have this problem though with low CYA even if I add stabilizer. Currently have stabilizer in sock in skimmer dissolving. I have an auto cover and pool water has not been open to sun except when cleaning. I typically add 1 gallon every other day in regular season with use.
As others have pointed out, the chlorine you are adding at best would only bring your FC up to 3.3. With low CYA and any organic matter in your water at all I would expect to see the FC at "0" by the end of each day.
How does the water look?
I'm going to guess with the cover it is, but do you have the bottom clean?
A pool exposed to the sun can easily have 3 - 4 ppm FC loss per day. My guess is you have something growing in teh water that is not quite yet fully visible and a SLAM may be in order.
- Jun 8, 2019
- 4,576
- Pool Size
- 20000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
Please add 10ppm of FC, let mix for 10 minutes with the pump on, then test the water and let us know what the FC is. (10ppm is about 3 gallons in your pool.)
That should give us an indication on if you have something going on or if it's just being burned off with a normal day of use.
That should give us an indication on if you have something going on or if it's just being burned off with a normal day of use.
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Have you by any chance preformed an Overnight Chlorine Loss Test to date? Even though you’re using a cover I personally would suspect this test will give you a clear picture what’s going on.