Disapearing CL

[Captweez]

Hi
This is my first post to the forum. I would be ever so grateful if someone could help me.

I have a 15,000 gallon above ground vinyl swimming pool. I have quite an unusual problem this season; I can't get the water up to chlorine levels.

I read the tips on PoolSolutions, and I am still puzzled.

My test results are
pH: 7.2
TC: (Result with OTO test, the DTP strips I have come back 0)
TA: 120
CYA: 45

When we took off the cover a week ago, the pool was green, we shocked it and ran the filter, and everything cleared up in two days. Then we added a chlorine floater, the disposable kind they might sell at K-mart or Meijer. We’ve had good luck with them in the past. A day went by, and the pool water showed no chlorine, so I added another floater. In theory the pool is getting double it’s recommended dose now. Still no Chlorine. Last night I added 2 gallons of 10% bleach. Today…. Nothing. The water looks beautiful, as clear as I’ve ever seen it, but I just can’t get a chlorine reading.

In the last week we’ve been to multiple pool places to have them test the water, at first they said all my numbers were ok, and it just needed more chlorine, but then they had me add stabilizer, then they had me add Alkalinity increaser because they said with low TA you can’t get a chlorine reading. (Somebody please verify this is crap, because I thought it was).

I thought the problem might be too much of it, but my OTO kit even shows it low.

Does anyone have any suggestions, and is it safe to swim in this pool despite the fact it has low chlorine readings?

[duraleigh]

Whether you can see them or not, you're still killing organics in your pool. Chlorine is consumed by the Sun and organics. You've got a nice level of CYA in there for Sun protection so the only thing left is organics.

Your problem is not unusual but, in fact, the single most common problem on the forum....you need more chlorine.

Test your Cl level at dusk and add enough Cl into the pool to bring it to 15ppm. Test again before the Sun hits it too hard tomorrow AM and, if it has dropped much below 14ppm, you are killing organics. I would continue to do that until your cl stays up overnite. Since your water looks so good, I don't think that'll be long.

Meanwhile, put a couple of jugs of Clorox in there if you want to swim today...you'll be fine.

Yes, the deal about T/A was bull hockey. However, you got it to 120 which is just perfect.

[geordie]

If you are floating two disposable chlorinators with trichlor in it, keep a very close eye on your ph. If you are using trichlor in large amounts your ph will drop quickly when they start to dissolve because it is very acidic.