Product review (5 stars): We have really crappy surface water now. These help a lot.
I swap them out every three months. Flush with at least a gallon of water when replacing. Its only harmless carbon if you don't fully flush.
They work fine. We have really crappy surface water now. We previously had 23 deep wells and excellent water.
These filters make things bearable for drinking purposes.

The Woodlands, Tx.