New white flakes coming out of the returns - Scale from SWG?

[stevet1]

Ok, so about 1.5 weeks ago, I started to notice some white flakes in one corner of the pool. There were only a few, so I ignored them. However, as the sun got stronger, I needed to increase my SWG output, and then I noticed that the flakes were now coming out of every return. They are paper thin, whitish flakes that are extremely brittle, and average 1/2 to 1 inch in rectangular shape.

The only changes over this period of time are: 1) I replaced the manifold for my Autopilot recently, and the acid feed is now going more directly into the center of the water stream, as opposed to just entering the side of the plumbing as it had been before. 2) My pool chemistry has remained fairly constant, except that around the same time as the flakes started to appear, I did raise my TA from 60 to 70 with baking soda. When my TA was 60 (and it had been there for at least 2-4 weeks), I hardly had any acid demand. Once I increased my TA to 70, there is a tendency for pH to rise to around 7.8, and my acid feeder has been going off fairly regularly. 3) increase in SWG output

Here are my current #'s

pH 7.7 <-- this is where my pH control is set to
FC 3.5
TA 70
CH 420
Borates around 40-45
Salt 4000
CYA 50

I raised the CH to >400 intentionally to partially compensate for the lower TA levels. What do you experts think is causing the flakes in my pool?

 

[JasonLion]

They are probably calcium flakes coming off the plates of the SWG cell. The pH is much higher around some of the plates, which can result in calcium scaling. The unit will reverse the polarity every several hours, which will flush the calcium off of the plates and into the pool.

The simplest thing you can do is to lower the pH set point down to 7.5. I would expect the number of flakes to go down dramatically, or stop completely, when you lower the pH. If that works, a longer term solution would be to lower the CH level somewhat.

It is not crucial, or even desirable, for the saturation index to be exactly zero. The pH is much higher at some locations inside the SWG, raising the saturation index in those locations. Having the saturation index slightly negative in the pool can prevent calcium scaling inside the SWG, which can increase the life of the SWG cell.

 

[stevet1]

I think I see the problem. Also since the SWG water temp. is significantly higher after coming back from the solar panels, the saturation index is even higher in the SWG. I think I'll just lower the pH for now and see if that solves it for the rest of the summer. If it can wait till winter, the rain should be able to dilute down the CH for me. Thanks again!.