I've been running with the TFP method since opening my pool this summer. I get what I'm supposed to do for my setup, and have been following faithfully. But I always wonder why, when SWGC is just another method to add chlorine besides dumping in bleach, would the CYA levels vary?
From what I can find searching on this topic, SWGC manufacturers usually recommend a specific CYA range. I've also read that they have to maintain higher CYA to protect the FC that is generated since it is generated in such small amounts. Which all makes sense, but does not explain why a target you'd target 5FC with 70ppm CYA when a non SWG pool would target that with 40ppm CYA.
If the issue is that with SWG you are running closer to a minimum, but getting away with it because you are constantly adding chlorine, then I should be able to get away with the same recommendations by using my stenner to constantly add chlorine throughout the day, rather than dumping a bunch in once or twice per day.
The CYA/chlorine chart page just says that "Most SWG pools appear to prevent algae at lower FC levels" but gives no indication as to why. If it's the salt, then the salt I added for "feel" should allow me to run with lower FC levels too...but the fact that EVERYONE told me to run my pool as normal when I did the salt thing made me think that must not be right.
So, can someone tell me more definitively why a SWG pool can maintain lower FC levels at higher CYA levels?