New Pool Owner - Chlorine not holding

[PoolDoc]

I have a pool that ends a season with around 50 ppm CYA and starts the next season with 0 ppm. Ben, how does a pool owner know which of the three situations you described above the pool comes under: nitrogen gas, nitrates, or ammonia? If the CYA was converted to ammonia, would there be a smell?

It's possible to test for both nitrates and ammonia, but we haven't checked to see which kits are reliable. We probably need to look for some ammonia kits, maybe from the aquarium side of things.

As far as I know, a kit is the ONLY way to tell if CYA has gone to nitrates. During startup, a pool that has lost CYA over the winter should be behave pretty much the same, regardless of whether the CYA went to nitrogen gas, or nitrates.

However, the tell-tale for ammonia will be rapid conversion of added FC to CC, followed by lost of chlorine: like this:

PM: Add 10ppm FC
Later, PM: FC-5 ppm, CC-3 ppm
AM: FC 1 ppm; CC 2 ppm

(not actual results, but typical of what we're seeing)

One very IMPORTANT fact to remind people of: when they add chlorine, they are NOT wasting it. Rather, they are getting rid of the ammonia. Also, without actual ammonia testing, the only way to tell when you're done (or getting close) is that the FC:CC ratio will get larger and larger, and the loss overnight will diminish, so you might see this:

PM: Add 10ppm FC
Later, PM: FC-6 ppm, CC-1 ppm
AM: FC 4 ppm; CC 1.5 ppm

(not actual results)

[AnnaK]

Thanks a lot for the clarification.