50+ Gal of bleach in 2 days and FC is still 1

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J

jmann

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May 21, 2008
7
Ok, first post, here goes...Sorry, it is so long...

A friend of mine recommended TFP and the BBB method last year, and I am only just this year implementing. I had some trouble with the filter last year, fuzzy water, lots of DE in the bottom. I ordered a whole replacement grid. Water cleared up, but I got algae. Followed the PS recommendation, and shocked and treated with algae chemical. Algae went away (as far as I could see). The rest of the year I battled chlorine. Being a non-BBB at the time, I didn't understand why my test strips showed no chlorine and the drop test showed off the chart. I now understand that the one was measuring FC and the other TC. I even spent $200 on 50lbs of lithium with no effect.

My pool is 20x40, vinyl lined, with DE filter, copper solar panels. I have an automatic cover that stays on all the time, or else I will have lots of critters floating in the skimmers in the morning (14 baby frogs in one skimmer is my record). I live in Kansas, and have only had about 2 weeks of constant sun so far this year, but it will stay sunny from now on. The pump is on a timer, from 8am until 6pm. I also have had a "death by puck" automatic feeder running for 3 years, and I immediately turned it off when I read that was why my CYA was off the chart.

This year before I opened, I read tons of posts, ordered my test kit and opened the pool. Here are my opening day readings:

Chlorine (drop test) 0.75
PH (drop test) 6.00 (best guess since it was so pale)
Free Chlorine 0.50
Combined Chlorine 6.5
Total Alkalinity 60
CH 600
CYA 110 (best guess as the water was about .2" from the 100 mark)

The pool calculator recommended I add Borax, baking soda, and of course bleach. I added

Borax: 20 lbs
Baking Soda: 24 lbs
Bleach: 4 gallons

Now before you tell me what I did wrong with adding all that baking soda, I already figured that one out. When I went back and read about CYA and the only way to reduce it was to drain, I went ahead and drained about 1/3 of the water (at least 2 feet) and refilled back more than I started with. The night I finished filling (it took 3 nights of after work filling), the CYA was only down to 100. Since then the past 2 days have not improved:

Yesterday:

Chlorine (drop test) 0.75
PH (drop test) 7.0
Free Chlorine 0.5
Combined Chlorine 3.0
Total Alkalinity 140
CYA 100

I added 11 gallons of bleach (all that I had on hand) and started aerating to get the PH up. I went to the store, and when I checked the water again 3 hours later these were the readings:

Free Chlorine 1.0
Combined Chlorine 3.0
Total Alkalinity 140

So I added 14 more gallons of bleach, trying to shock.

Tonight when I got home this was my reading:

Chlorine (drop test) 0.75
PH (drop test) 7.00
Free Chlorine 0.50
Combined Chlorine 3.0
Total Alkalinity 140

So I added another 16 gallons of bleach trying to get it to shock, and turned on the slide and pointed the returns up to aerate.

2 hours later, my readings were

Free Chlorine 1.0
Combined Chlorine 6.0

So I added the last of today's purchased bleach, which was another 14 gallons.

Just now, another 2 hours later my readings are

Free Chlorine 1.0
Combined Chlorine 2.0

I've put the pump on 24 hours. I haven't rechecked CYA because I read that it takes about a week for it to settle.

I have two main questions: Is there such a thing as too much bleach? According to the pool calculator, it should have only taken about 14 gallons of bleach to get my shock level up to 25. Why hasn't 50+ gallons over the last 2 days made any difference? Second, why hasn't my TA dropped with such a low PH level?

My husband wasn't confident in my switching to the BBB method, he was upset about me draining out 1/3 of the pool, and now I've poured 50 gallons of bleach in the pool with nothing to show for it. Do I keep adding bleach?

Oh, one more question, When I read that I want to get the shock level up to, say, 25. Is that the FC level, CC level, or the TC level?
 
I think you have a testing issue. You aren't going to get numbers like .75 on a chlorine test. If it's FAS-DPD, you get either 0.2ppm or 0.5ppm per drop, depending on your sample size.
 
If the Free Chlorine (FC) and Combined Chlorine (CC) measurements are correct, then I'll bet that you've got a lot of ammonia in your pool and the CC is chlorine combined with ammonia (forming monochloramine). Did you have a higher CYA in the pool before closing for the winter and did you let the pool go over the winter (i.e. no addition of chlorine)? If so, then soil bacteria may have converted some of the CYA to ammonia and that takes a LOT of chlorine to get rid of. You can get yourself an inexpensive ammonia test kit from a pet/fish/aquarium store. It will take about 10x the ammonia level in FC to get rid of it and around 1x the CC level to get rid of that. It may be better to do another partial drain/refill of the pool since your CYA is still high anyway and that will dilute not only the CYA but also any ammonia as well as CC. Nevertheless, you may be looking at a lot more chlorine in your future...at least the ammonia test will tell you how much.

Richard
 
WOW that's a lot of bleach! I am not sure how to much bleach it would take to damage a vinyl liner, but I am sure it can eventually. I know to much shock will. I witnessed that first hand and it wasn't pretty.

GL in getting the pool straight. WIth patience and the wonderful people on this site you'll have a TFP in no time too!
 
chem geek said:
I'll bet that you've got a lot of ammonia in your pool and the CC is chlorine combined with ammonia (forming monochloramine).
Click to expand...

I was just reading about this on another post. I will try to find one tomorrow. What is an acceptable level of amonia?
 
jmann,

I had to wait for chem geek before chiming in on that post. I think he is very likely correct (about the ammonia). That's pretty rare but has apparently happened to one or two folks who posted here and Richard (chem geek) was the one who diagnosed the situation correctly and got them eventually straightened out.

I would suggest that you follow his advice carefully. Your situation is very unusual and few of us have the background or experience to handle it successfully. As painful as it may sound right now, the drain and refill once more may be your best bet.

BTW, I was born and raised in Leavenworth, KS. I still come back to hunt with my cousins every year. Not too many pools out your way compared to the South or TX or CA.

Welcome to the forum. Keep the faith and your pool will get cleared.
 
jmann said:
What is an acceptable level of amonia?
Click to expand...
Unfortunately, zero, as any amount of ammonia will immediately combine with chlorine. You cannot have Free Chlorine (FC) in a pool exist with ammonia. So it has to be removed -- either physically through dilution or through breakpoint oxidation (superchlorination) with lots of chlorine.

Richard
 

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chem geek said:
jmann said:
What is an acceptable level of amonia?
Click to expand...
Unfortunately, zero, as any amount of ammonia will immediately combine with chlorine. You cannot have Free Chlorine (FC) in a pool exist with ammonia. So it has to be removed -- either physically through dilution or through breakpoint oxidation (superchlorination) with lots of chlorine.

Richard
Click to expand...

But how much chlorine is to much before it will damage the liner?

A few years back when I was trying to clear up my Moms i/g frog pond and I mean colonies of frogs/tads. :lol: pecan leaves, etc. I was scooping and scooping to remove all the organic materials as possible. Because all the chlorine was disappearing within hours of going in. I come over the next day after pouring about 14 bags of shock and the pool liner was split in each corner and I mean big splits! :shock:
 
judging by the drop in FC 2 hours after you added the 14 gallons, the bleach is being used up practically as soon as it hits the water. So at this point, I would say damaging the liner is probably not imminent.

However, at some point, the chlorine usage will slow, and a 14 gallon slug of bleach 'could' be bad.

Keep testing and using the calculator, and you will get your pool cleared right up!

Welcome to TFP!
 
The key question is what is the FC level, not how much chlorine did you add. If there is ammonia you can add vast amounts of chlorine and not damage the liner, but if there isn't any ammonia you can add a medium amount of chlorine and ruin the liner. Test the FC level and add enough chlorine to bring the FC level up to shock level then wait half an hour to an hour and repeat. That way the FC level never goes above shock level and there is no risk to the liner.
 
I am draining the pool again this morning (hubby was NOT happy). This morning when I checked, my CYA was down to 80 and FC was 1 and CC was 2. So I will check everything this afternoon again including the ammonia, consult the pool calculator for half my normal water level, and then start shocking. My plan is to get it down below the shallow end and then shock this smaller amount of water until I get a shock FC reading. Then I will refill. I'm hoping it will be easier and more cost effective to only treat 18,000 gallons instead of 36,000.
 
You should not drain a vinyl liner pool lower than one foot of water in the shallow end!!! The liner can shrink as the water is removed and then tear when you add water and it needs to stretch out again.

One good test is to take a 5 gallon bucket of pool water, add 1 oz of 6% bleach, wait an hour, test the FC level and if it is below 10 repeat the process. The number of oz of bleach you use doing that can give you an idea of how much chlorine it will take for the entire pool.
 
lulupalooza said:
But how much chlorine is to much before it will damage the liner?

A few years back when I was trying to clear up my Moms i/g frog pond and I mean colonies of frogs/tads. :lol: pecan leaves, etc. I was scooping and scooping to remove all the organic materials as possible. Because all the chlorine was disappearing within hours of going in. I come over the next day after pouring about 14 bags of shock and the pool liner was split in each corner and I mean big splits! :shock:
Click to expand...
The big difference between your current situation and your Mom's frog pond is that the frog pond did not have Cyanuric Acid (CYA) in the water. So initially the added chlorine would quickly combine with ammonia to form monochloramine (a Combined Chlorine) and after all the ammonia got converted, then additional chlorine would have broken down that monochloramine (to nitrogen gas after a short while), but additional chlorine after that would have just stuck around (as Free Chlorine) and been VERY strong because there was no CYA in the water to moderate it's concentration (intensity).

In your current situation you have two big differences. First is that you can measure the amount of ammonia to get an idea of how much chlorine will be needed. Second is that you have a lot of CYA in the water so any extra chlorine will be mostly bound to CYA and not react with the liner of anything else -- the amount of disinfecting chlorine will remain relatively low.

Finally, you know how to add chlorine to a pool carefully -- namely to pour it slowly over a return flow with the pump running and then to lightly brush the side and bottom of the pool where you've added it to make sure it thoroughly gets mixed.

Richard
 
I bought an ammonia test kit at Petland ($). It tested to 0.6 mg/L, which was the lowest value next to 0.0.

I followed the advice to treat a few gallons to see how much I would need. I added bleach and an hour later my Fc was 25, exactly my target for CYA of 100. Hoorah!!!

It's two hours later now, and it is back down to 14. Here are my current numbers:

FC 14.0
CC 3.5
PH 7.0
TA 120
CYA 100
Ammonia 0.6

I've added more bleach. My new question is how long do I need to keep the FC up at 25?
 
If you added 1 oz of 6% bleach to a five gallon bucket of pool water that is about the same as adding 96 ppm of chlorine to the pool. If I remember, your pool is about 36,000 gallons. Raising FC by 96 takes about 55 gallons of bleach in a 36,000 gallon pool. The actual number may be somewhat higher or lower because of measurement imprecision in the bucket test.
 

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