Fluctuating FC

Nillawafers

Member
May 24, 2019
11
San Gabriel, CA
How much is too much? Last week I SLAMed successfully, although I ran out of reagent which was backordered - I got the new reagent and tested last Friday, everything was within range, .5 ppm CC. I had been adding around 2-3 cups of bleach blindly during the week I was waiting for my reagent to show up.

Now, almost a week later and not as blindly, I am noticing my FC is fluctuating, how much is normal? I have been testing at mostly the same time. My kids swim everyday, and each morning I add enough to bump the FC to the top of the parameters (7 ppm) and in the morning it is without fail 3-3.5 (at the bottom). This morning it was closer to a 2/2.5 ( it was very slightly pink before I added another drop to clear it).

How much fluctuation is normal? I felt the SLAM went pretty well, and the algae that was showing up on the bottom has not shown up for 4-5 days now. I am adding 3 cups a day and pretty much struggling to keep it within parameters (this morning it was below).
 

Agua

Member
Aug 17, 2018
10
Taylor Mill, KY
I have 22,000 Gallon Vinyl. I measure cl every evening and raise it to 8. I average 2-5 ppm drop in Cl each day. I add anywhere from 50 to 100 oz 10% Cl each night.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
15,653
Tucson, AZ
What’s the % of the liquid chlorine you’re using?

24oz (3 cups) of 10% LC raises your FC by 5.7ppm whereas 6% bleach would only raise it by 3.5ppm.

You have a very small volume pool (3,300 gallons) and it sounds like a fairly high bather-load. Typical chlorine loss per day is 2-4ppm but in your situation with shallow water, low volume and sunshine, it can easily be higher.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
21,201
Laughlin, NV
FC loss will fluctuate. How sunny it is, how many bathers you had, did any one pee in the pool, etc. That is why it is best to target the upper end of the FC range for your CYA.
 

Nillawafers

Member
May 24, 2019
11
San Gabriel, CA
What’s the % of the liquid chlorine you’re using?

24oz (3 cups) of 10% LC raises your FC by 5.7ppm whereas 6% bleach would only raise it by 3.5ppm.

You have a very small volume pool (3,300 gallons) and it sounds like a fairly high bather-load. Typical chlorine loss per day is 2-4ppm but in your situation with shallow water, low volume and sunshine, it can easily be higher.
It’s 6% bleach. I have been adding what pool math suggests each time. I raise it to the top, I just worry when I test in the morning and it’s below parameters that it’s low enough that something will take hold KWIM?

I’m not complaining haha, just worried about it dipping below what it should. Is there anything I can do to prevent that? Besides maybe shading the pool more or something?

ETA: would raising it above (slightly) parameters be detrimental? So that it stays within parameters longer?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
21,201
Laughlin, NV
ETA: would raising it above (slightly) parameters be detrimental? So that it stays within parameters longer?
You need to raise the FC enough that it stays above the minimum FC for your CYA. As Matt said, small pool volume, high bather load. Add more bleach each night. Increase it to a full quart and see how it goes. Or get 10% from Walmart.
 

Nillawafers

Member
May 24, 2019
11
San Gabriel, CA
Okay that sounds like a plan. Perhaps I should start testing at night also so I can get an idea how much FC I am losing after kids are in the pool. Otherwise it seems pretty stable and clear.
 

Agua

Member
Aug 17, 2018
10
Taylor Mill, KY
I have tried to maintain too low a level of chlorine in the past so now I error on the high side. Like I said I start at 8 and let it fluctuate down from there. Since I started that routine I have had no algae Problems.