Just installed a chlorine generator, and have discovered that my pool has a HUGE chlorine demand problem. Honestly, I haven't been that diligent in measuring the demand before, just added Chlorine tabs to the feeder to keep the pool from getting green. Was constantly adding it, shocking, etc....just thought that was how it was. But now, since installing the SWG two weeks ago, I've been looking closely at the chemistry, and discovered this huge demand. Here's the breakdown of the chemistry, pool details are in my sig:
Salt: 3100 ppm
Free cl: 0.0
Total cl: 0.2
Total Alkilinity: 68
Water Temp 87f
I have recently done a partial drain because the CYA was off the charts, I believe it was at about 150-200 because I drained off 66% of the volume and now it's 53. This was from the constant addition of stabilized tablets/shock before the SWG was installed.
Since the SWG, I have not been able to measure any chlorine via test strips, confirmed by pool store testing. But the water is crystal clear, and the SWG is producing as it should (clear cell, can see the cl fog). Here's what I know about the demand:
Last night, raised the free chlorine to 20ppm with Calcium Hypo. Tested with strips to 10ppm by half dilution so I could read the level, then doubled the amount (ended up being a total of 73 oz of 78% Calcium Hypochlorite). This morning (8 hours later), I measured 1ppm Total Chlorine, and 0ppm Free Chlorine.
I have no visible algae, no cloudiness. The only anomaly I notice is a small amount of dark dust-like substance on the bottom. This was worse before the partial drain, so that may be left over fallout of whatever it was (I vacuumed on waste what was there before installing the SWG two weeks ago).
I'm at my wit's end here... Any help is appreciated!