an insulated watering system is provided for fowl , animals or the like in which a length of pipeline is defined by several groups of watering pipes with each group of watering pipes being of a different wall thickness and having greater heat - insulating efficiency in the direction of water flow . the pipes are preferably formed from foamed polymeric / copolymeric material , such as polyvinylchloride , and each includes an interior cylindrical closed cell core sandwiched between noncellular skins or plies . the exterior diameters of all watering pipes are identical , but the interior diameters of the various groups decrease in the direction of water flow . in this fashion , a larger wall thicknesses of the pipes effectively insulate the lesser volume of water flowing through the water line along downstream portions thereof .