You don't need to guess when to change the filter, as the cartridge will just shut down when its lifespan will be over.

Normally, the filter capacity is same as indicated on specification. But it's also depends on how dirty does the water you filter.

1. Take the perforated cap off from the bottom of filter

2. Flush UF membrane (white silk yarn you can see) by tap water for few seconds

3. Spin-dry the filter by hand

4. Store filter in cool and dry place

1. Pry small plastic cross piece out.

2. Take the dirty PP cotton out & put a new one.

3. Put small plastic cross piece back to it.