Phosphates?

[chem geek]

Charlie,

What is your pool's Cyanuric Acid (CYA) level and what was the Free Chlorine (FC) level before you found that the SWG wouldn't produce chlorine when the phosphate level went up? It is possible that the FC level was too low for the CYA level so the chlorine was getting used up fighting algae and the SWG couldn't keep up. Did you notice the water getting dull or cloudy when the SWG couldn't produce chlorine fast enough?

Did the manufacturer of the SWG give any sort of explanation for this? Did they say anything about phosphates directly interfering with their SWG?

I've been looking at getting to the bottom of what's going on with phosphates at this thread and so far it looks like one has to get to a rather high phosphate level above 3000 ppb before Ben's chart doesn't work as reliably. Most SWG pools are able to keep away algae and operate effectively with an FC level that is at least 4.5% of the CYA level up to around 3000 ppb in phosphates, but for a pool owner with 4000-6000 ppb in phosphates, they needed to keep the FC level closer to 7.5% of the CYA level which is the minimum level recommended for manually dosed pools. This is why I'm interested in your pool's FC and CYA levels and if you noticed the water getting dull or cloudy.

Richard