Choosing a whole house in-line water filter can be a daunting task. Understandably, any time a home owner looks at laying out a substantial amount of hard earned money, he/she wants to be sure they get the right product. Carbon based water filter systems typically use replaceable filter cartridges. Consider the number of cartridges (more cartridges means better filtration but also means more cost to replace those filters). free refrigerator water filter replacement Not all filter cartridges are created equally though. Different companies offer cartridges with different life expectancies. Ask how much water will be filtered before the cartridges need to be replaced and calculate the cost on a cost per gallon of water filtered basis.