Chlorine block continues

[Chemist101]

I need help desperately. Last end of season I had CYA readings above 150-200. I drained 1/2 pool twice and added endless chemicals.
This year I opens pool and the CYA shows 0. Tests twice. Yet my chlorine is still blocked. I've added 12 gallons liqui shock and nothing. Then 5 gallons of bleach and nothing.

My readings are 0 CYA, saturation index -0.5, TC 1.9, FC 0, pH 7.3, total alkalinity 107, total hardness 105.

Water is crystal clear and 30,000 gallon in ground liner pool. Cartridge filter an heat pump. Use auto chlorinator with 3" pucks.

What should I do? Do not trust pool store at this point.

[chem geek]

Check the ammonia level in the pool with an ammonia test kit from a fish/pet/aquarium store. Also check the Combined Chlorine (CC) level with a chlorine test kit. I suspect that bacteria converted the CYA into ammonia over the winter and that's creating the huge chlorine demand. If all the CYA were converted to FC, then it could be huge since it's roughly 2.5 ppm FC required for every 1 ppm CYA that gets converted. You can read about my personal experience with this issue in this thread and can learn the chemistry of what is going on in this thread.

[Chemist101]

Thanks for response. So assuming I have ammonia present and last season the CYA closed at 125, how much chlorine is needed?

[chem geek]

If all of it converted to ammonia, you're looking at somewhat over 300 ppm FC cumulatively added to get rid of it. Let's hope that didn't happen and that the bacteria converted at least most of it to nitrogen gas instead. Get an ammonia test kit to see. If that kit tests in ppm N units, then multiply by 10 to get the cumulative FC you'll need to add (at a minimum -- it could be more if there's also partially broken down CYA such as biuret).

[Chemist101]

So ammonia test shows 1ppm so not horrible.
Also brought water back after adding some alkalinity the prior night.
Shows 0.5 TC, 0 FC, 54 CYA...the rest is ok.
Plus water tested positive for nitrates of 29.

I drained 1/3 or more of pool. Waiting to refill then will start adding shock. What does it mean to add 10 times amount of ammonia? How much chlorine is that in gallons if liquid or pounds if bags? Should I be adding bleach, regular shock, lithium shock, liquid shock,etc?
Thanks

[chem geek]

1 ppm N of ammonia would need 10 ppm Free Chlorine (FC) to get rid of it. So just shock to 10 ppm FC, then see if it holds, if not add some more, see if it holds.

Since you already have CYA in the water, use chlorinating liquid or regular unscented bleach. If you have money you want to throw away you can use lithium hypochlorite. If you use Cal-Hypo, then that increases Calcium Hardness (CH) as well and if you were to use Trichlor (usually pucks/tabs, but also comes in granular) or Dichlor, then those increase Cyanuric Acid (CYA).

You can use The Pool Calculator to calculate dosages.

[blah blah blah]

Do yourself a big favor drain all of the water & refill as you are wasting money & time, its just plain bad to try and fix this with someone who just wants to talk chemicals when the D&R is all you need.

[Chemist101]

30,000 gallons is a lot to drain though.

I'm finally getting chlorine reading now. Not sure how much as I did t take to store yet.

When you say to add chlorine to 10ppm, does that mean keep addonh until I get such a reading even after I get any reading? So I reading is 4pm, still keep adding?

[blah blah blah]

If you were given the correct info to drian & refill the first time & not do half refills this problem would have been gone already. Your water was junk and needed to be drained everything is not chemicals when you have reading that can only be fixed by draining the water. But go buy a ton of chlorine with a bill that will keep rising.

[chem geek]

Testing with an ammonia test kit to get an idea of how much chlorine would be needed is reasonable and he did that and it showed a low number. Had he shown a large number, I would have suggested water replacement, or at least mostly water replacement. As shown in this post, when bacteria converted CYA into ammonia (and some partially oxidized CYA) in my pool, it took 56 ppm FC to get rid of it. Now that was a 16,000 gallon pool and chlorine cost me $3.50 a gallon. So a little more than 7 gallons cost me around $25.

And now that he's getting a chlorine reading he's nearing the end. And he needed to do a partial drain/refill anyway because his CYA level was too high.

Yes, raise the FC to 10 ppm and see if it holds there. If it holds overnight, you're done. During the day, you'll lose some from sunlight, but at your CYA level you should lose less than half over a long day. After you've got things under control, you can read the Pool School to learn more about maintaining your pool.

[Guest]

Thanks for the suggestions. After 1/2 refill and fixing the problem of high phosphates by adding chemical for that and then cleaned out filter 48 hours later, the pool is back to normal.

You can be sure I will be testing more frequently to maintain better.
The hardness is a bit low but I was told that's not really a problem and to leave it since it will naturally rise from chlorine as season goes forward.

[scottgriffin]

I would check the ammonia level. See what that reading is and if that doesn't work than I wouldn't know what else to do. I guess you could try getting some new inground pool liners. My friend had a similar scenario and he switched out his liner and his problem went away. He got his liners from http://milliespoolandspa.com/ but there could be a build up of chlorine or other chemicals that are behind the liner.