CYA and Lifetime of Chlorine

[chem geek]

I got a response from Janet saying that the depth of her pool is 3.5 feet in the shallow end to 8.5 feet in the deep end (hopper shape with a long gradual slope). This is deeper than many pools with a 3 foot shallow end and a 6 foot deep end so could help explain why the higher CYA shows such a dramatic shielding effect in her pool. It should show this effect in the 6 foot pools as well, but would be more pronounced in a deeper pool. Her pH is usually 7.4 but tends to drift up towards 7.8 (I asked that since chlorine is more protected at lower pH). I think we're getting somewhere!

So now we just need to see if the SWG effect has anything to do with efficiency of the SWG cell or if it's just an issue of increased protection of chlorine from sunlight. That's not an easy test to do unless someone hasn't yet added high CYA levels to their SWG pool and is willing to increase those levels (and measure the SWG output rate overnight before and after the increase in CYA).

Richard