I have a 27000 gallon salt pool with an Aquapure 1400 SWG, a DE filter. A few weeks ago, I noticed that my total chlorine was low. I increased the SWG to 100% and am currently running it 12 hours per day. The highest I can get my total chlorine is .6 and what is coming out of the hose from the SWG is 1.5 when it is running. I have checked the chemicals and the pool store has too. Everything seems to be within normal limits. The CYA is at about 65. I was told that my four year old SWG was probably at its end, so I replaced it. The problem continues though. I've checked the voltage at the SWG, and it is at 26v (which is what it should be). One pool guy told me it was the phosphates (at 500). From what I've read, phosphates at 500 aren't really that high, and there's no obvious algae anyway. Another pool guy told me that I need more CYA, even though CYA at 50 was more that adequate for my pool for the past 4 years. I shocked the pool heavily last week, and the total chlorine eventually returned to near zero. Any other ideas?