First I thought it might be having too much iron in the pool water but the stains are not that bad. I treat it once a year and flush all the water out, although it has been nearly eleven months, since the treatment. I find it hard to believe I have that much iron in solution that it could give a weekly loss of 5 ppm, or maybe one does not need 20% maybe a lower percentage can have an effect, any thoughts?
I know this is hotly debated and some have proposed that it is due to a combination of high FC levels and high temperatures, my FC is 4.6 -5, my target CyA is 30 but I am beginning to think that it is a combination of factors as follows; the pool is 10,000 gals. And yes I am adding 6.8 oz of CyA every week. Strangely though it seems to stop or slow down significantly at the 25 ppm level, as my daughter would say "Go Figure". This is truely baffling.
The pool is covered, that might have some effect, so the average temperature is around 83 F, that to might have some effect, and the FC is as descibed above. My friend's pool, 20,000 gals, also losses about 5 ppm per month, not however per week. Originally we thought this was happening over a 3 month period but now his is one month and mine one week, we use to test for CyA once every three months. His pool is uncovered and the average temperature is 78 F, otherwise his specs are as mine; our pH is 7.5.
This is a mystery before I had a SWG I used the BBB method and never had a problem. I am beginning to think that maybe as the SWG superchlorinates some water and the temperature is 83 F and that is the reason, but I cannot obviously say for sure. My pool is shallower at an average of 4 ft 2 inches than my friend's which goes down to 6ft 6 inches. All I do know is it is driving me crazy.
This is for info only but from searching "CyA loss" it seems I am not alone, in fact we could form a club or group. There must be some similarities among us all maybe someone might like to create a database of conditions.
I have a PoolPilot Digital SC-60 set at ORP 690 and power at 2. It has a diverter slowing down the flow through the cell my friend has the 1400 which does not have a diverter, maybe the longer lingering of the water in the cell has an effect, but here again this is only a thought, I have no way of testing or knowing. But if others who have this issue have diverters it might narrow down the usual suspects.
Would adding a puck help, if so how much CYA does it release and how many days before it dissolves completely, and is there any downside?
I could of course live with it as it seems to slow considerably at 25 ppm, by lowering the calcium to achieve the same Calcite Saturation Index (CSI), but at 25 ppm I seem to lose a lot more FC than I do at 30.
As I am nearly at the point where I do my once a year iron drain I might do it now and see if that helps. I will advise in an update once I have time to do it and my wife is gone for the day because she thinks I'm crazy to drain the pool, she might be right, then again I might discover the culprit, who knows.