I am not sure about regular concentration camps but in the extermination camps (Auschwitz, Majdanek, Chelmno, Sobibor, Belzec and Treblinka) the water the prisoners had access to wasn't safe to drink. Prisoners had to rely on the daily soup and/or tea or coffee rations (or what passed for those) for their fluid intake and sometimes suffered from extreme thirst. Access to the non-potable water that was available was also extremely limited. Some privileged prisoners at Auschwitz had access to showers but generally there was hardly any way to keep the body or clothes clean which led to appalling hygienic conditions that in turn facilitated the outbreak of diseases.