You need to desalinate the urin. There are filters that do this (http://www.equipped.org/watrfood.htm#SeaWaterIntoFreshWater).
The ads for the First Need filter state that it doesnīt desalinate. So you canīt use it to turn urin into drinking water. Thatīs also true for the other filters for just purifying water.
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If it isnīt broken, it doesnīt have enough features yet.