Need help with pool that won't hold chlorine

[Guest]

I have been having this problem for over a month. My pool turned real green when I was on vacation. I used the things the local pool supply company sold me and it did clear the green up and some more things to clear up the cloudy water. Now when ever I test the chlorine it show 0. The pool supply kept telling me I have nitrates in the water between 1 and 2. They kept selling me shock by the case and telling me to keep shocking the pool. I have dumped over 50 pounds of shock in the pool and it stall will not hold chlorine and they say it still has nitrates. I have been doing some reading on this forum and I am trying to switch to bleach instead of shock and have purchased my own test kit. I can add bleach and get the chlorine level up to 5.5 first thing in the morning when I test it, but by noon it is back to 0. This morning when I tested it before day light it was at 7.5 and now when I test it 10 hours later it is back to 0.5. Just looking for any ideas why it will not hole the chlorine. Everything else seems to be within range and the water is very clear.

FC 7.5
CC 0
TC 5.5
PH 7.5
T/A 140
CH 250
CYA 60

It is a 14000 gal above ground pool with a sand filter. Not Salt water.

Thanks for any ideas
Keith

 

[Bama Rambler]

Which test kit did you get?

Your best bet is to do an OCLT (overnight chlorine loss test). That'll tell us if it's algae eating your FC (which I suspect it is).

 

[frogabog]

Check the pool calculator, for 60ppm CYA your minimum is 5, target is 9, shock is 18. I think you may be missing the boat by a few ppm.

Test, and then dose to 9ppm tonight, test again tomorrow morning. If you loose more than 1ppm overnight you haven't finished the shocking process.

If you still need to shock, just use bleach and maintain shock level till you pass the overnight test with no more than 1ppm loss. Save the powdered shock product for when you need to raise CYA someday.

 

[frogabog]

FC 7.5
CC 0
TC 5.5
PH 7.5
T/A 140
CH 250
CYA 60

oops... something's wrong here. FC is 7.5 and TC 5.5? You sure that's not switched? Cuz if it is (and it has to be, TC number should either be equal or greater than FC), you've got 2ppm CC, not 0 and you are 100% for sure not done shocking.

 

[Guest]

I did write that down wrong. The TC was 7.5.

 

[Bama Rambler]

That says you have a CC of 2, that means you need to shock.

 

[Guest]

Thanks for the advice. I will shock some more.

 

[mynewpool]

I have dumped over 50 pounds of shock in the pool and it stall will not hold chlorine and they say it still has nitrates.

For the pro's, would 50 lbs of shock added to the pool still put the cya at only 60 or would it be much higher?

 

[Bama Rambler]

I think I misunderstood something.
Is your FC and TC both 7.5 ppm? If it is then there may not be a reason to shock. You can run the OCLT to be sure if you think there might be.