Water, Sickness caused by drinking contaminated:
There are many forms of sickness that can be contracted by drinking contaminated water. There are also many ways to penalize a person with sickness.
The G.M. must determine if a character will contract a sickness (on the character sheet there is an avoidance-roll for SICKNESS).
If the chance for sickness proves positive, you must then decide how bad the sickness is. You decide this based on the durability of the character.
The more constitution and strength a character has the better chance he or she will have to overcome sickness.