The red/green shift is to show that the direction of the current has switched and it happens every few minutes. If you only look at it now and then, the odds are 50/50 that you will see the same color.
It has NOTHING to do with PPM.

When the LED turns OFF, the batch is done.
A gallon might take 24 hours...or more.

Ken


At 07:22 PM 7/15/2012 -0700, you wrote:
Hi Ken,

Just want to ask, i own a silver puppy, when i set a gallon of distilled water to brew, its light turns green. After around four + hours it turns red, when i check the ppm it is only 3.5ppm (water before brewing is 1.5ppm). So in all that time i only made 2ppm? Then i shut it off, and when i restart it, it turns green again. The setting is always at manual-auto. Is this a normal occurence in brewing one gallon? How long should a one gallon normally brew?

BTW, the electrodes are super clean and so with the jar and round plastic for distance.

Thanks.

Melly