Water is essential for nearly all body functions including temperature regulation, absorption of nutrients, waste excretion and tissue growth. Over 80% of the body of a newborn piglet consists of water, compared to about 55% in a finisher. Severe water deprivation may result in death; even minor dehydration can result in reduced feed intake, lower daily gain, poorer feed conversion, reduced milk production and lower weaning weights. When performance problems are being investigated feed is often analysed, but the water supply is frequently overlooked.