Sediment Filter Safety without 5 critical heavy metal, Safe Filtering Item certified and endorsed by NSF The contaminated substances like the rust and impurities precipitated due to the water pressure are used to be deposited or stockpile d into the filter block. Thus the water pressure will be dropped and the filter needs to be replaced with a new one. Of course the filter can be used for the more time if the water pressure maintains a normal condition even though the contaminants deposited into the filter case. However if the filter color has been faded into the darkness it should be replaced with a new one. If the filter shell keeps the color for ananti-bacteria it is distinguished from the white colored one without an anti-bacteria