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[PoolDoc]

For each ppm of chlorine added with dichlor or trichlor, you'll add nearly a ppm of stabilizer. With trichlor it's a bit less, with dichlor a bit more.

Regarding the relationship between chlorine and CYA, read the "Best Guess" page linked in my signature.

[TexasGolfer]

Thank you, I've read through that post numerous times, and many others, but I'm not seeing what I am looking for. Also, I saw where Watermom indicated the 10 to 6 relationship of chlorine to CYA in trichlor. I think what I am not making clear is that I'm trying to estimate what the impact will be before I put the pucks in, to determine how many to start with. For example, with bleach we have the calculators that tell me if my pool is a certain size, I need to put in a certain number of oz of bleach to raise my FC level 1 ppm. So my question is, how can I estimate the rise in FC and CYA from one puck of trichlor? Also the drop in pH?

I know that it takes time for these pucks to dissolve, and once they have done so, the CYA is already in the pool, and difficult to remove. I've also read that it may take several days after it's put in to register, which has me worried that even if I take them out, the level could keep rising. I want to sneak up on the desired level, and not have to worry about shooting way past it. So if one puck has the potential to raise my CYA by 10 ppm, then I'll just put in one at a time, and then test several times after it's dissolved. But if one puck is only likely to raise CYA by 1 ppm, then I'll put in 5 or 6 at a time, and not be so worried about shooting way past my goal.

[TexasGolfer]

Okay, a more thorough Google search turned up this thread which has the math I was looking for:
http://www.poolforum.com/pf2/showthr...f-tri-clor-add

Converting for my pool volume, looks like one 8 oz puck will increase my CYA by 2.7, so the four I have in my floater right now should be about right to start with. I'll pull it out at night for the purposes of doing my overnight FC drop test until I'm completely done fighting algae.

[JimK]

......I've also read that it may take several days after it's put in to register, which has me worried that even if I take them out, the level could keep rising......

I don't think this is true. Once it has dissolved it should be measurable and won't keep rising, unless you add more. I think where the confusion may be is that when adding stabilizer granules separately (those who use unstabilized sources of chlorine need to add stabilizer separately) it takes time for those granules to dissolve, and so the stabilizer level will rise as the granules dissolve. Personally, I find I get a good stabilizer reading about 24hrs or so after adding stabilizer granules directly in the skimmer and running the pump the whole time (the granules get caught in the filter where they then dissolve).

So measure after the pucks dissolve to see if you need to keep adding stabilizer.

Certainly someone here will correct me if I'm wrong.

[CarlD]

No, I actually think JimK is right and it's a subtlety. CYA granules take a very long time to dissolve but Trichlor fundamentally contains CYA so as it's releasing chlorine, it has to be releasing CYA, too, and acid.

[BigDave]

FWIW, dichlor (if you can find it pure) adds 9 ppm CYA for every 10 ppm FC and, unlike trichlor pucks, dissolves very quickly. One gotcha when starting new water is the sun will strip the FC quite quickly until the CYA has built up.

[TexasGolfer]

Cool! That makes sense. Thanks guys.

[TexasGolfer]

Thanks to you good folks here, the pool appears to be in great shape. Last time I added bleach was Wed night. I'm using triclor pucks to try to increase my CYA, but I can't get it above 30 yet. After adding nothing but triclor, here are my numbers this morning:

FC: 7.5
CC: 0.5
pH: 7.4
TA: 100
CH: 325
CYA: 30

Almost identical to what I posted on the 27th. I should note that I turned the pump off for about 8 hours last night for the first time in two weeks. It kicked back on about 2 hours before I tested.

So my question today is, should I just keep going with the triclor pucks, or use something else to up the CYA without raising the FC? I assume that 7.5 FC is too high for the long term.

Thanks!