Chlorine Locked?

[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'

[chem geek]

We don't really know if the 1 pound per 2000 gallons (5 pounds per 10,000 gallons) is the proper dosage. While it looks like it might work for reesie's situation, it looks like aciam's situation is more severe. At any rate, for this dosage rate this translates to 3.4 pounds (1 55-ounce box) of Arm & Hammer Super Washing Soda and 11 cups (about 3 quarts; 3/4 of one gallon) of BaquaShock per 10,000 gallons.

I suppose one could start with this sort of dosing and then measure the pool water after 24 hours to see if there is still CC in which case one can add more.

[reesie]

My husband and child wanted to swim over the weekend so we waited until 4:00 pm today to add the washing soda and BaquaShock. I tested before we added them.
fcl 3
tcl 5
ccl 2
alk 170
cya 30
ph 7.5


I tested again at 9:00 pm
fcl 1
tcl 1
ccl 0
alk 200
ph off the scale

Chem_geek and Waterbear said wait 24 hours and start adding chlorine, if it's 0 ccl, until it holds a fcl reading. Lower ph before adding chlorine or after? How much chlorine should I add at a time and how often? I have cal hypo and 3 inch tablets and bleach ( if the store doesn't run out again!).
Then clean filter thoroughly and change sand.
Again, thanks for the help! All of you guys are the best!

[reesie]

I tested 0 fcl and 0 tcl and 0 combined chlorine so now I'm going to start adding chlorine. Any advice as to how much to add at a time and how often?

[chem geek]

You'll want to add Cyanuric Acid to the water as well as chlorine or else sunlight will break down your chlorine too quickly. Your 3" tablets will add both chlorine and CYA, but will take too long to add either. The Cal-Hypo is fine if your Calcium Hardness (CH) isn't high and the bleach is also fine. So you'll need to get some pure CYA or perhaps could get some Dichlor which dissolves quickly and can be added to give you both chlorine and CYA (at least some) initially. Up to you -- whatever is easiest for you to get. Most people get pure CYA and put it in a sock or panty hose to hang over a return or in the skimmer for faster dissolving (some add it slowly to the skimmer to get caught in the filter, but that usually takes longer to dissolve).

If you have some CYA in the water, you can get your FC up to around 3 ppm to start with, not more than 5 ppm, but just note that it may drop quickly initially until you get more CYA in the water so you'll probably be adding chlorine multiple times per day the first day or two.

[reesie]

I have good news and bad news...I think. I don't have any combined chlorine so far. But I also don't seem to be having any luck at getting my free chlorine or total chlorine levels up.
My cya is 60
ph 7.6
alk 150
the most I've gotten the fcl to is 1, tcl was the same
I've added 16 ozs. cal hypo (65%) at a time
Tonight we added 24 ozs.
Should I go ahead and change the sand now or wait until I can get it to hold a fcl reading?

[waterbear]

Change the sand! There is probably a lot of gunk in their creating the chlorine demand.