waterbear said:
duraleigh said:
But you have to look at the total volume of high FC level liquid being added to the pool. The liquidator is still a 'drip feed' of this superchlorinated resevoiur. In a SWG the entire amount of superchlorinated water is being added to the pool.
I don't think it works that way since the output from an SWG is only a somewhat higher ppm FC than the general pool water, not 80 ppm. Though the FC level "between the plates" may be 80 ppm FC, clearly all of the water isn't going through that area since it would emerge out of the cell at 80 ppm FC if that were the case. Instead, I think that a small portion of the water through the cell is exposed to the high FC levels with the average of the bypass water and the water in between the plates being the fairly low ppm FC higher (4-10 ppm FC, most likely) that emerges from the cell as a whole and through the returns into the pool. A 2 ppm FC loss per day to be recovered with an SWG at 20% on-time and one turnover of water per day would be 2/0.2 = 10 ppm FC. If the output were 10 ppm FC higher than a starting 4 ppm FC in the pool water, then the 80 ppm FC in between the plates would be with x*80 + (1-x)*4 = 10, x=7.9% of the water volume.
Now there IS a difference even in the small super-chlorinated water volume between an SWG and The Liquidator. With an SWG, the chlorine generated is done so in very acidic conditions (near that plate) so the hypochlorous acid concentration is extremely high. In The Liquidator, the high FC is at high pH and the hypochlorous acid concentration is much lower. I estimate that the 80 ppm FC in the SWG would be nearly all hypochlorous acid closer to the chlorine generating plate (even with CYA, at low pH it would still be 40+ ppm hypochlorous acid), while in The Liquidator, the same 80 ppm FC would only result in a hypochlorous acid concentration of around 2.3 ppm since the pH would be 8.83 (I also assume CYA in the water). If 50 ppm Borates are used, then the pH would be 8.19 and the hypochlorous acid concentration around 8.1 ppm. These are still very high numbers -- remember that in pool water with an FC 10% of the CYA that the hypochlorous acid concentration is only around 0.05 ppm (equivalent to 0.1 ppm FC with no CYA). The water in the Liquidator is exposed to this elevated chlorine level for a longer period of time, but it's a lower volume of water (rate of water flow) compared to the SWG. Again using the one turnover example, but a "100% on-time" for The Liquidator while the pump is running, one needs 2 ppm FC of 80 ppm FC mixed with the pool water so that's x*80 + (1-x)*2 = 4, x=2.6% of the water volume.
The bottom line is that both manual dosing or using The Liquidator with a hypochlorite source of chlorine exposes the water to lower peak chlorine levels than in an SWG with this latter exposure time being very brief. Of course, that's the theory. We'll still need to see if this really matters in practice.
Richard
