Well THIS is a new problem . . .

[feetr2c]

First off, I am not new to pool maintenance. Kept two Intex pools sparkling and balanced, and this will be my 4th summer on a 24 x 52 AGP round REAL pool lol. After uncovering a month ago, I had the usual dirty water. It sat uncovered a month or so at about 2/3 full, so green algae took hold. Yesterday, I dumped 7 pounds CYA in a pillow case, tied it around a hose, and topped off the pool with the remaining 1/3 of its capacity. By the time it was full, the CYA had dissolved, as the pillow case was empty (no it wasn't ripped). I did not test for FAC, since the pool had sat idle all winter, and then uncovered and in the sun for the last month prior to top-off. I super-chlorinated last eve to 30 ppm with 12% liquid Sodium Hypo, as I do every spring for the last several years. 1.5 Hayward LX Pump and 175 Lb Hayward sand filter ran all night. This morning, no evidence of green. But of course water is cloudy and can barely see the bottom. I can clear that up with some Baquacil Floc, following the filter-aide directions, again, as I do every year. This is where it gets strange. This morning, I collected a water sample and sat down at the kitchen table with my Taylor K-2006 kit, which uses FAS-DPD. My FAC test showed 30 ppm. Brand new reagents and DPD powder this year. This truly baffled me, as all the other years, that 30 ppm super shock decreased to less then 5 ppm by morning. Ph showed to be 7.4 or thereabout (ph can be difficult to pinpoint with a comparator, but my sample did not have that wild purple color that would clearly show a way high ph). Just for kicks, I put in a drop of acid demand reagent...No change. Then another...and another... 12 DROPS LATER, I saw the first visible color shift showing a now corrected reading of 7.2. This normally happens with just one or two drops. I then moved on to TA and found a reading of 125 (raw, not taking into account cyanurate correction). Strangely, my TA color shift went from green to an endpoint of a funky orangeish color instead of the usual red. My CYA test was 70 -- I know a bit high, but I usually start the season around there, as we can get a lot of rain here, plus more backwashing during pool start-up etc, so by mid summer, my CYA is typically centered within the 30-50 range. My question...can a high chlorine level of 30 ppm cause such screwy things in the other tests? I know that very high chlorine can 'bleach' out reagents, but face it, 30 ppm is exorbitantly high. Also, how in the heck can a green pool maintain a 30 ppm super shock? CYA doesn't protect chlorine from depletion from a high-demand 'task', but rather from breakdown/"evaporation" due to sunlight. Any thought? Anyone? Bueller?

 

[duraleigh]

Also, how in the heck can a green pool maintain a 30 ppm super shock?

It can't. There was an error introduced somewhere. Organics consume chlorine and your pool had a ton of organics so chlorine was consumed.....that's pretty undeniable.

You could repeat all your steps and try to find it if you like or you could just chalk it up to "one of those things" but I am certain you had a good bit of chlorine consumption.

 

[Bama Rambler]

Did I read correctly that this morning was the first time you tested anything??

What was your CYA before you added to it?
If your FC was really 30 ppm your pH is wrong. You need to test it again once the FC is below 10 ppm.

I too suspect an error somewhere.

 

[feetr2c]

I did not test CYA before adding, as it typically drops off to nothing over the winter with end of season drainage and lots of rain and drain cycles, etc. This morning was indeed my first test. After a full day in sunlight, I retested this eve, first with a dip strip, then my Taylor kit. The strip showed all in range with the exception of FAC. That patch was a deep purple -- high. My Taylor test showed FAC at 20.5, CC 0, pH 7.2, TA 115, TA corrected 97, CYA 70, CH 220, Sat -0.5

Finally I have some meaningful numbers, I'll test FAC again tomorrow eve. It's almost as if the liquid chlorine was stronger than 12%. The label actually says 12.5%, but that half a percent shouldn't matter enough to create whatever was going on this morning. I would think it impossible for the pool to still have had FAC from last season.

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[Bama Rambler]

Since you didn't test before you started adding stuff you don't really know what the starting point was. You really should have tested before adding anything. But that ship has sailed.

What does the water look like?
Are you going to do an OCLT?

 

[feetr2c]

The water has cleared significantly! It is virtually colorless, save for the brilliant blue that the liner imparts. I'm on my way to a great pool!

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