Each tablet converts 1 litre of unsafe water into 1 litre of potable water. They are relatively rare and serve only to speed up an otherwise identical method of purifying water. Their condition will degrade over time very slowly; tablets with the same condition level will stack in the inventory. Condition does not affect conversion rate. Note: it is more time effective to use these directly from your inventory rather than at a fire - it will take approximately one in-game minute per tablet compared to ten.