Specifically, I'm talking about this product here…
It has an LED that blinks when the water is running. It blinks red, yellow, or green to indicate filter quality (maybe) – but it seems to have no power source. So, my specific question is what powers the LED? And, I would also like to know what it's measuring?
It is frustrating to Google this because people don't seem to care how things work, and the phrase is equal to "What does it do" and all I can find is "It shows you the water quality" – well, that's not how it works. Brita claims the filter lasts for 100 gallons, but I'm not sure about that, it seems as though the LED turns to red based on the amount of time, but to do that it would need a constant power supply and I don't see one.
Best Answer
If an average faucet flows at 2 gpm (according to the US EPA), and the filter does not significantly reduce that flow, then 100 gallons is about 50 minutes.
An inexpensive CR2032 is rated at 230mAh, which is more than enough. Chances are it's something even cheaper like a stack of a few LR44 button cells. That can also be used to retain information.
The other options (electrochemical action, paddle wheel generator, miniature nuclear reactor) would be too expensive or would cause contamination.