Chlorine Locked?

[reesie]

Here are the readings tonight.
7:00 pm
fcl 0
tcl 0
ccl 0
added 1/4 tsp. bleach

8:00 pm
fcl 0
tcl 0
ccl 0
added 1/4 tsp. bleach

9:00 pm
fcl 2.5
tcl 2.5
ccl 0
added 1/4 tsp. bleach

10:00 pm
fcl 4
tcl 4
ccl 0
added 1/4 tsp. bleach
That's going to be it until tomorrow night after work.

[chem geek]

Oh my gosh! This might actually be working!!! This is great news. 1/4 teaspoon of 6% bleach in 2 gallons would normally raise the FC by 10 ppm so I'm not sure what's consuming so much chlorine after you start measuring it. The reaction with the remaining hydrogen peroxide should be fast which explains the first couple of hours of readings, but after that I would have expected chlorine addition at 9 PM to register more like 12.5 ppm at 10 PM. At least you aren't getting CC readings.

[reesie]

Tonights readings:
6:30 pm
fcl 2.5
tcl 2.5
ccl 0

7:30
fcl 7.5
tcl 7.5
ccl 0

8:30
fcl 10
tcl 10
ccl 0

9:30
fcl 15
tcl 15
ccl 0

Most of these tests I performed 2 times to double check
No combined chlorine in any of the checks!
So what now?

[chem geek]

Well now you can use sodium percarbonate in your pool. I think you just got the pH Up and hydrogen peroxide, neither of which will be in sufficient quantities for your pool. So you'll have to buy sodium percarbonate. You can get it at The Chemistry Store. As for how much to get for your 15,000 gallon pool, if you want to you could redo your experiment with a half-dose or even a quarter-dose. That might save you money. The dosage I had you do was roughly 1 pound per 1000 gallons. That would be 15 pounds or about $40 worth of sodium percarbonate. I suspect it won't take that much. If you redo the bucket experiment (you don't need to wait as long now that we know that the CC is eliminated in less than 8 hours), then that could save you money if you find you only need half or one-quarter as much -- up to you.

[PoolDoc]

Richard, can't she just buy "washing soda" at Walmart and "BaquaShok" at her pool store?

[waterbear]

Richard, can't she just buy "washing soda" at Walmart and "BaquaShok" at her pool store?

I would think that it would work since the net effect of adding sodium percarbonate is adding hydrogen peroxide and sodium carbonate.
The only thing is that the baqua shock is a 'stabilized' peroxide (most likely stabilized with citric acid) but I would think the sodium carbonate would raise the ph enough to destabilize it.

[reesie]

I will do whatever you guys think is best.
We have let the chlorine levels drop in the pool for the last week and we have been swimming. We haven't had any ill effects. The combined chlorine has been lower lately. The funny thing is since several days before we started swimming, we have not smelled any chlorine smell outside, not even at the pool. When I tested the pool 2 days ago, the combined chlorine was 2 and the fcl was 5.
Today the fcl was 3 and the ccl was 0. Several days ago, my cya was low so I broke up a 3 inch tab and put it in and put another tab in the floater since I didn't have any stabilizer except in the tabs. I thought my combined chlorine would go through the roof when I put the tabs in but so far so good.
If I need to get the sodium percarbonate and dry acid, where would I get dry acid?
Follow the procedure and then clean the filter, replace the sand and hopefully, we're good to go!

[chem geek]

Richard, can't she just buy "washing soda" at Walmart and "BaquaShok" at her pool store?

Yes, Arm & Hammer Super Washing Soda (careful: NOT the laundry detergent) can be used for the "pH Up" sodium carbonate and "BaquaShock" can be used for the hydrogen peroxide. However, to dose this properly, we need to know the concentration of hydrogen peroxide in the product. From this link, it says it is 27% hydrogen peroxide. So remember what I wrote earlier that by weight, 1 pound of sodium percarbonate is 0.675 pounds sodium carbonate and 0.325 pounds hydrogen peroxide. So 0.325 pounds hydrogen peroxide is 1.2 pounds of BaquaShock. If I assume a density of around 1.1 g/ml, then 1.2 pounds of BaquaShock is around 17-1/2 fluid ounces or a little over 2 cups.

So let's use the 1 pound sodium percarbonate per 2000 gallons amount so for 15,000 gallons this would be 5 pounds of washing soda (sodium carbonate) and about 4 quarts of BaquaShock. The washing soda will raise the TA by 38 ppm and could raise the pH to 8.8 but the BaquaShock will lower the pH as it oxidizes whatever is left in the pool. Hopefully you don't have a lot of metal in your water since the higher pH could stain. So add this recommended amount of washing soda and BaquaShock and wait 24 hours with the pump running the entire time, though technically you saw results in your bucket test after 8 hours. You should then measure zero CC. You'll then need to start adding bleach until you get an FC reading.

[PoolDoc]

Hey Chem_Geek, Waterbear;

If you can work this out as a recipe - so many boxes of A&G washing soda and so many jugs of BaquaShok per 10,000, it could potentially help a bunch of people.

Just sayin'