Chlorine / CYA

[Jbonnette]

That makes sense . It sounds like a higher ppm might be the best thing for me being that I live in Louisiana and just recently converted to SWG. My pool is partially shaded by a couple of large trees though and I haven't been losing chlorine too badly so I might see how well the SWG can keep up before using 70+ ppm. It seems like you would want to run lower chlorine levels if possible for swimmer comfort...

[chem geek]

Actually, while in the water itself the main rate of oxidation of swimsuits, skin and hair is proportional to the FC/CYA ratio so there shouldn't be much difference between 3 ppm FC with 40 ppm CYA vs. 6 ppm FC with 80 ppm CYA. However, when you get out of the water, it is the FC level that matters in terms of how long it continues to react with your sweat to form chloramines that can smell so from that point of view you are correct that lower would be better.

Remember that the FC/CYA ratio relates to the rate of the chlorine reactions while the FC by itself relates to the capacity or available reserve of chlorine so how long it will continue to react once you leave the pool. And yes, as the water evaporates when you leave the pool the concentration of chlorine increases which is probably why the higher FC levels are associated with faster fading of swimsuits -- it's not a rate issue (i.e. not FC/CYA related), but a capacity issue once you leave the pool.

[aylad]

I live up near Shreveport, and after a few years of trial and error, I find that a CYA of 80 ppm is ideal for my pool, and I end up using much less chlorine with the added benefit that I don't have to add it every day, like people who run lower CYA levels do. It's not so bad now, but I think you'll find that when late June/early July gets here, you'll have trouble keeping the Cl from going to zero during the day. However, once the CYA is in the water, drain/refill is the only way to reduce it, so you're smart to just raise it as far as you need to in order to have acceptable chlorine loss. You can always raise it later!

Incidentally, you might check the owner's manual for your SWG--many require CYA levels in the 70-80 range for proper operation and to maximize cell life...

Janet