Patent ID: 8790512

Claim:
A liquid filter for filtering a source liquid, comprising: an indicator device comprising: (i) at least one erodable member positioned in the liquid filter to be in contact with a source liquid; (ii) an indicator member; and (iii) a visual indication arrangement; wherein said erodable member is configured to: (a) be gradually eroded by interaction with the source liquid or with an element within the source liquid and (b) have an erosion profile that correlates to an extent of use of the liquid filter, wherein the indicator member is configured to: (a) be gradually displaced by a change in size of said erodable member and (b) allow the source liquid to flow through the liquid filter when the indicator member is displaced to an end state, wherein the end state is when the erodible member is completely eroded; and wherein the visual indication arrangement is configured: (a) for directly viewing said change in size of the erodable member or (b) for directly viewing a gradual displacement of the indicator member.