Green water. High CYA

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i'll get another reading in a few hours to see if the 38% loss rate holds. currently projecting a 6 day fall to the sub-3ppm level to try bio-active:

$ bc -l
38
38
last*(1-0.38)
23.56
last*(1-0.38)
14.6072
last*(1-0.38)
9.056464
last*(1-0.38)
5.61500768
last*(1-0.38)
3.4813047616
last*(1-0.38)
2.158408952192
 
You do not always measure CC when there is algae because the chlorine can combine with the algae and the CC is stuck in the algae so not measured in the test kit. This is especially true if the algae is clumped and not disperse.

I would NOT wait 6 days before adding the Bio-Active. Your algae problem may get very bad by then. If you really want to try the Bio-Active, then you need to dechlorinate quickly now. That's why I referred you to the hydrogen peroxide, but if you want to get a dechlorinator (usually sodium thiosulfate) from a pool store instead, you can.
 
It's possible that stuff is OK, but the Baquacil Oxidizer link I gave was for 1 gallon of 27% hydrogen peroxide for $17 so that's 63 cents per % per gallon whereas what you found is $64/35/2 = $0.91 so 91 cents per % per gallon so quite a bit more expensive.
 
That entire Q&A is bogus:

Q: I have a plaster pool – What is the effect of CYA in plaster pools?
A: Multiple studies have now confirmed that CYA levels over 100ppm is damaging to pool plaster surfaces. If pool water has elevated CYA levels for extended periods of time the plaster surfaces are degraded and become porous and often abrasive to the touch. This is a key reason why it is important to manage CYA levels in plaster surfaced pools. In pools with porous plaster surfaces CYA can become immobilized in the plaster and when Bio-Active™ is first applied this CYA is released back into the water. For this reason starting levels of CYA in these pools is often under reported on testing and can be much higher than the pool owner realizes. Very high starting levels of CYA can require multiple treatments with Bio-Active™ to bring CYA levels down to the safe range.
Click to expand...

The "studies" they refer to are really just one Arch plaster study where they did NOT control for carbonate alkalinity. So they kept the same TA level as the CYA level was higher and that resulted in lower carbonate alkalinity so a lower saturation index and THAT was why the plaster degraded. High CYA levels are NOT degrading plaster. What happens is that continued use of Trichlor lowers the TA over time and if one adds baking soda to adjust it one may not add enough if one targets a TA level even as the CYA level climbs. So one ends up with less and less carbonate alkalinity so one no longer saturates the water with calcium carbonate and the plaster degrades.

As for whether porous plaster surfaces hold CYA, I find that doubtful -- at least no more CYA than the amount of water in the porous area which would be small. The question would be whether sufficient amounts of CYA bind to any pool surfaces at all, be it plaster or piping, and do so in sufficient quantity to be measurable. Again, this is doubtful. If the surfaces were melamine, that would be another story. :crazy:
 

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Hydrogen peroxide will react with chlorine to lower it by converting chlorine to chloride and producing oxygen gas. The pH will drop some from chlorine usage/consumption.

As for the pH rise, if you didn't add anything to the pool then that usually occurs from carbon dioxide outgassing from the pool but not usually that fast so something doesn't seem right about it. Did you take a sample too close to the surface, especially if the pump wasn't running? If so, then that could just be a local reading, not a bulk water reading.
 
The quart of hydrogen peroxide lowered the FC to ≈13.5 in under an hour. Chemistry FTW ;)

The pH was still 7.7 so I added a small glug of HCl.

I'll let the sun bake it tomorrow and buy more H2O2.

If 32oz (@7.5%) consumed 6ppm, that's 0.4oz of H2O2 per ppm (let's say ½oz/ppm), so I'd need 5oz to get to Bio-Active range. (Or 10 pints of drugstore 3% ;)

- - - Updated - - -

BTW, the pool "smelled more like chlorine" during the first half hour after adding the H2O2.
 
This evening it was 11 FC (0 CC, 7.4 pH). I added 7 pints of drugstore 3% (≈3.4oz H2O2) which I expected to lower FC to 3ppm, but actually only lowered it to about 8. I wonder of some of the nonlinearity is CYA releasing chlorine? I'll test in the morning.
 
This evening i measured ≈6FC (0CC, 7.2pH) and added another 6 pints of 3% (≈3oz H2O2) which I expect to get me at or below 2ppm FC. If that works out, I'll measure CYA and add the Bio-Active. Don't wanna jinx myself, but the water is clear right now.
 
after an hour or so of mixing, FC was down to under 2ppm. I measured the CYA. I started at 1:7 dilution (1/8) with distilled water b/c that's what i'd needed last time to get an in-range reading, but it was clear all the way up the tube. I tried again at 1:1 dilution (1/2) and got ≈55, so ≈110ppm!?!? Have I been visited by the Magic CYA-Eating Algae that i've seen on the TFP forums? Have my reagents gone stale? I added the Bio-Active anyway b/c i had it and i'll track at least daily, but man, I am weirded out. Could the H2O2 be messing with the CYA measurement? I assumed it was used up, but...?
 
I doubt you had high enough chlorine for that to be the case, but have noticed over time that cya readings reported in some threads seem to bounce around during a slam, so its hard to say what's going on, or if the hydrogen peroxide is also skewing he readings too.

When you contracted the algae, had the FC zeroed out at any point? If so, it IS possible you created your own source of CYA-eating bacteria...

Either way, I'm just chiming in to say my fingers are crossed for you that the reading is true and your water stays clear ;)

If your water stays clear and the bio doesn't work/or te lw cya readings are false, at least you then have the option of R/O ;)
 
Today (1 day after Bio-Active added) ≈1.0FC, ≈0.5CC, 7.3pH, ≈100CYA, 76°F.

Added a glug (≈10oz) of standard 10% pool NaClO.

- - - Updated - - -

Water's still clear! (Fingers still crossed. Thanks!).

What's "R/O"?

Re: FC zeroing out, no, I don't think it did, but since efficacy (ORP?) is so low with a ton of CYA, the 2-4ppm I had might not have counted for much.
 

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