Chlorine loss at a RAPID rate :(

[wildchilde]

HI,
This year I drained my pool, reset a leg or two and refilled it. The past few weeks I cannot keep chlorine in it at all. It goes in a matter of hours. I'm full sun from probably 11:00 am till the sun drops past the trees maybe 5:00 to 7:00 depending on the month. I do my own testing and also take to the pool store every now and then. I just got a 5lb bag of CA and put in there, helped it dissolve to speed the process up a bit. I do not have a CA test so I got some of those ghastly strips and depend on the pool store for that. I think it's in my sig but if not then here's the pool info also.

24ft round intex w/ swg. they say it's 12500 gallons.
Pentair test kit and a walmart (regeant) kit, strips for kicks and grins.
my readings today before lunch.
tc 0
fc 0
ph 7.6
alk 140
cya 30-50 (strip)

This is a bit before noon I add about 3/4 gallon of 10% liquid chlorine wait about an hour then take a test to the pool store for testing. I tested and of course it was high well above the 3.
Pool store says......
alk 180 doubt that
ph 7.6
calcium hardness 70 (added 20lbs of hardness)
chlorine 4.
cya 100. That can't be. The only stabilzer that is in there is a 5lb bag.
low salt they say so I added 2 bags of salt.
I"m not that worried about the salt thing because I'm in full sun so much that little swg intex supplies just can't keep up the demand. Guess i need some trees.....
My ph and alk have a little bit of a float cause when I add water from the faucet it's so off the charts I have to add acid every time to bring it back down.
I clean the pool, add the stuff, get in float for a bit, get out piddle then for kicks and grins I just went out about 30 minutes ago and tested the chlorine... low and behold it's already dropped to 2.
Just hubby and I, no neighbor kids in pool recently.
It's bugging the Crud outta me how the chlorine can leave so darn fast!! I've had this pool 4 years now and never this bad.
I will say... the past four jugs of chlorine are a different brand that Atwoods has started carrying. Could that be it?

 

[jblizzle]

I do not really see in your post a time frame for a large loss in FC.

If you just added the CYA, it may not be fully effective yet and the sun may be burning off more FC than you are accustomed to.

 

[JasonLion]

It would be a huge help if you had your own top quality test kit. Pool store testing is notoriously unreliable, and what you are seeing is not consistent with their test results, so I tend to very much doubt their test results.

5 lbs of CYA should have raise the CYA level to around 25. However the recommended CYA level with a SWG is between 70 and 80. So you will be losing chlorine far more quickly than the SWG can possibly keep up with. With CYA around 25, I would expect you to lose about 3/4rds of your starting FC level each day, which seems to fit more or less with your description.

 

[wildchilde]

I put chlorine in this morning maybe bout 11:00. tested again this evening about 4:30 so in about six hours I had a drop of 50%.
I've got two, three tests if you include the strips. One is a Pentair DPD for chlorine, the other, (also a reagent test) oto for chlorine from walmart. I wanted to see just how much they would differ if any.
How different can the reagents be?
Neither pool store here is reliable, I have taken the same water to both stores one right after the other and they both told me different. not today but on a different occasion I did that.
I'll try getting some more CYA and adding to it in a couple days. there's been some in there all week but probably 1/4 of the bag i put in yesterday and dissolved it.

 

[Richard320]

You don't need to spend any more money on hardness increaser - your vinyl pool liner won't care if CH is low. Spend the dough on a test kit. I know...... but we're big on beating that horse around here.

Check the label on that chlorine. It may very well be weak stuff. My wife bought some store brand stuff that is only 3% !! But that's for the laundry.

If you had a FAS-DPD test kit, I'd prescribe an Overnight Free Chlorine Loss test. Since that ain't happening, all you can do for now is keep dumping the jugs in and try to keep it above minimum to prevent an algae bloom.

 

[JasonLion]

I put chlorine in this morning maybe bout 11:00. tested again this evening about 4:30 so in about six hours I had a drop of 50%.

That is sounds completely normal for relatively low CYA levels (somewhere in the general area of 20 or 50, depending on how much sunlight hits the pool)

 

[wildchilde]

I will get some more CYA then. What is the FAS part of the FAS-DPD test? I have the DPD tablets in the Pentair kit.
I'm in full sun from mid morning to after 6:00 most of the time. Keep the CYA about 80 then? I have put 5lbs in so I will try 2.5 more.
Thanks!!

 

[jblizzle]

The FAS-DPD test is a much more accurate way to test the FC and CC that uses a powder and can read upwards of 50ppm levels. It is not based on matching colors, but by counting drops until the color changes.