One question we need to ask ourselves when buying a water filter system: Is it CERTIFIED be able to filter harmful materials in your water? If not, why buy even if it is cheap?

Even though some filter claim that they can filter contaminants up to 0.01 micron, but it never mention how much is the capacity. I have seen reports some filter can filter 0.01 micron for the first 100 liters water, after that only managed to filter 1 micron for another 300 liters and subsequently as good as useless.

Therefore, it's important to buy a filter with documentation how much water it can filter and what is the quality of the last drop of water in that capacity.