FC | 11.0 | 12.0 |
CC | 1.5 | 0.0 |
TC | 12.5 | 12.0 |
pH | Not tested | |
TA | Not tested | |
CH | 175 | 250 |
CYA | 30 | 30 |
S | 4800 (assumed not tested) |
Regarding your chemistry table, I would use more CYA, probably 50 ppm to 70 ppm and FC at 5 to 10. The FC is going to need to find it's way into the cover vault and guides, so I wouldn't go below 10% of CYA. That's just an opinion with no experience to base it on, but I can't imagine that circulation will be great in there. It might be worthwhile to figure out a way to force pool water exchange into there, and I thought of you when I fished a mega-monster-pump-action-ninja-diehard-rambo watergun out of the pool this morning.I guess the more often it deploys/retracts will be the best help.
With respect to water balance, I would not add additional CH to go any higher than 250 until you've had time to observe how your chemistry fluctuates. Replacement water will always be carrying a bit in, and it will only exit via overflow. I raised mine to 325 ppm and I regret it, but it's certainly manageable.
The amount of hypochlorous acid (HOCl) in water with Cyanuric Acid (CYA) at typical pool pH is proportional to the FC/CYA ratio and is orders of magnitude lower than the FC level itself. The primary oxidizing and sanitizing compound is hypochlorous acid while hypochlorite ion and the chlorinated isocyanurate compounds (chlorine attached to CYA) have orders of magnitude lower oxidizing or sanitizing capability
Cyanuric Acid (CYA, aka stabilizer or conditioner) is used in pools to protect chlorine breakdown from sunlight. Though CYA absorbs ultraviolet (UV) radiation directly thus shielding the lower depths of water and protecting chlorine in those depths from breakdown, the primary result of having CYA in the water with chlorine (hypochlorous acid) is that it combines with chlorine to form a set of chemical species collectively called chlorinated isocyanurates. These compounds also absorb UV without breaking down as quickly as chlorine. The full chemistry is complicated (well, tedious) because there are 6 different species of chlorinated isocyanurates (that is, chlorine attached to CYA) and 4 different species of Cyanuric Acid and its dissociated ions. There are 13 simultaneous chemical equilibrium equations of the CYA, chlorinated isocyanurates, hypochlorous acid and their combinations though only 10 of these are independent from each other.
At a pH of 7.5 and 77ºF (to be conservative), an FC that is at the minimum FC we recommend for manually dosed pools which is around 7.5% of the CYA level has the same active chlorine level as a pool with only 0.06 ppm FC and no CYA. That is not a typo. Fortunately, it takes a low active chlorine level to prevent algae growth.
However, to kill off already established algae, one needs a significantly higher chlorine level since it gets used up locally quickly and must penetrate algae clumps which takes longer to do so in order to get ahead of algae growth (reproduction), one needs a higher chlorine level. Though technically something like 20% would probably be enough to kill algae faster than it grows even in a bloom, it would take longer to kill off so we use an FC that is 40% of the CYA level as the shock level for clearing a pool of existing algae. This FC/CYA ratio has the same active chlorine as an FC of 0.6 ppm with no CYA
So a pool with 32 ppm FC and 80 ppm CYA has an active chlorine level the same as only 0.6 ppm FC with no CYA. So these high numbers are just that, high numbers, and the only thing actually "high" is the amount of chlorine in reserve.
Also the methods used by the industry assume you use the shock weekly model and buy algicides etc. if you like that model you can keep FC low and ignore CYA. You will likely at some point experience trouble if you do that. The name of the forum here is trouble-free
Nitrogen trichloride is the most volatile and irritating. The monochloramine odor threshold is 0.65 ppm (650 ppb); for dichloramine it is 100 ppb; for nitrogen trichloride it is 20 ppb. The equilibrium concentrations in air for monochloramine and dichloramine are somewhat lower than that in water, but nitrogen trichloride is extremely volatile so will not saturate the air before becoming extremely noticeable and irritating.
From the models, not using any CYA at all in any pool (indoor or outdoor) can result in far higher irritating nitrogen trichloride concentrations and also has the chlorine level be too strong for outgassing of chlorine (mostly hypochlorous acid), corrosion of immersed metal and oxidizing of swimsuits, skin and hair
I think thats is payback from you Caco...my head is smashed reading that![]()