Stabilizer Mystery

[chem geek]

You can read more technical info about this phenomenon in Degradation of Cyanuric Acid (CYA). You can also read about my personal experience with this in It Can Happen to Anyone - Zero Chlorine, CYA --> Ammonia.

[TonyPH12345]

Yesterday after I posted that, I added three gallons of 6% bleach to the pool. That was after I read 0 chlorine with both OTO and DPD.

24 hours later, a Color-match DPD is registering 2.0ppm FC and 3.0ppm TC.
An OTO test was WAY OFF the SCALE yellow. So I think the DPD is being influenced by HIGH chlorine, and in fact I still have chlorine after 24 hours.

The CYA test today is showing < 30ppm (it's cloudy, but the cylinder gets full before the dot completely disappears.)

Other tests:
- pH of 7.6
- TA of 120
- CH of 240

I'll keep testing each morning and see what happens with the chlorine now. I may have been "Crossing the Hump" as I called out for help.

[TonyPH12345]

Today, TC was back down to 1.0 with both DPD and OTO tests... 3 more gallons of bleach in... Pool looks lousy...

[aylad]

If the pool is green, then the chlorine is going to be consumed very, very quickly by the algae. The only way to get that cleared up is to get your chlorine level up to shock level (12-15 ppm) and KEEP IT THERE until the green clears up. If you shock it, then let the level come back down to 1 or 2 ppm, then it's not going to clear. Rather, the more consistent you are about keeping it up in the 12-15 range, the faster it will clear up. You need to add more chlorine to get the levels back up, at least 2-3 times daily, and more frequently if you can. Shocking is not a one-time thing...rather, it's a process that takes some time and sometimes LOTS of bleach. Keep that chlorine level up until the pool clears and until you're not losing more than 1 ppm of chlorine when testing after sundown and again before sunup.

AT this point, the CYA is not that important to getting the pool looking good--I would just concentrate on the chlorine.

BTW, your pump/filter needs to be running 24/7 through this, cleaning your filter as the pressure indicates. THe chlorine will kill the algae, but your filter is what will remove it from the water.........

Janet

[PoolDoc]

"24 hours later, a Color-match DPD is registering 2.0ppm FC and 3.0ppm TC. An OTO test was WAY OFF the SCALE yellow. So I think the DPD is being influenced by HIGH chlorine, and in fact I still have chlorine after 24 hours."

If you are describing these results accurately, you were measuring a pool with low FC and high CC. And, yes, high CC seems (sometimes) to show up as FC.

I've never known CYA to be metabolized that rapidly, but then I have no really info on just how fast it can be metabolized. But, it sounds like you've got an algae/bacterial soup that's eating your stabilizer (and turning it into ammonia) as fast as you can add it. My original recommendation (borax to 7.8 & 3 gallons of bleach each and every PM) was almost certainly the right thing for you to do. It certainly would help you resolve your green goo.

It doesn't sound like you've done that consistently.

Messing around with the CYA, TA, & CH now is more of a distraction, than an aid. You need to get the goo (and probably, the ammonia pooped out by the CYA eating bacteria) dealt with first, BEFORE you worry with the other stuff.

If you want to really understand, read Chem_Geek's articles. Otherwise, just do it.

Ben

[TonyPH12345]

Ben, I've given up on the DPD test. I'm measuring whatever the OTO test measures... Isn't that TOTAL chlorine? Ordered me a replacement K2006 since my previous one is "expired" and I'm out of FAS-DPD powder anyway.

At any rate, this AM I'm seeing OTO test off the scale again (water is almost brownish yellow after adding 5 drops).

Through this whole time, my attached SPA has not had a trace of algae in it. It was crystal clear and snow white as I wish my pool were... Odd, huh? But now it is developing what looks like metal stains...brownish orange deposits on the plaster... I've had that happen before and know how to deal with that, but I'm not going to touch that until this is resolved.

The "Algae" deposits are turning grey, and they're becoming easier to brush away. But what's under the brushed spots is not clean plaster... It's still green underneath. Other than adding this turbidity through brushing, the water is clear. So all the algae is clinging algae, not water-borne.

So right now I don't have a reliable way of measuring FC. In the mean time, if my math is right and I can assume the bleach is actually 6%, adding 3 gallons of bleach to 9000 gallons of water should raise FC by 20ppm, is that right?

Thanks, ya'll, for the hand-holding. We're only about 3 to 4 weeks away from Swim Season here in Dallas, and I'm sure hoping I don't disappoint my kids.

[PoolDoc]

If you've got 3 weeks, and your filter is functioning reasonably well, you should be fine.

Grey is dead; green is live. (tho, I think you'd worked that one out ;-)

RAISE THE PH!

Adding chlorine to ammonia in a HIGH ph solution produces monochloramine, which is GOOD at penetrating clinging algae. Free chlorine is not. Monochlor is what Yellow OUT leads to, IF you follow the directions. It does work; it just leaves a mess to clean up. But you've ALREADY got the mess, so no worries there.

But, if you don't raise the pH, you'll tend to produce di- and tri- chloramines which are stinkier and are NOT good for anything that I'm aware of.

20 ppm is about right. If you brush and stuff, it will drop very quickly. But, you should probably stay out of the "brown" OTO range. I think 20 is dark dark orange.

Ben