There is a removable, 3-layer microporous candle inside where the filtration process occurs, and is recommended to be replaced every 6 months or so. The innermo

There is a removable, 3-layer microporous candle inside where the filtration process occurs, and is recommended to be replaced every 6 months or so. The innermost layer is also activated carbon which the water must drip through to get to the bottom layer. I think you're right about some build up over time in the clay as it must retain some impurities. It's pretty common to clean it every once in a while to prevent that build up, at least that is what's mentioned by Brazilians that have used this filter for decades