ʻO ka pahu wai wela he cylinder me ka lalo conic. ʻO kāna hana ʻo ia ka hoʻomaʻamaʻa pololei ʻana i ka wai maʻemaʻe i ka mahana e like me ke koi ʻia e ka mahu ma hope o ka piha ʻana o ka wai hou i ka pahu. Ma hope o kēlā, hoʻopau ʻia ka wai hou i loko o ka Tricanter a me Centrifuge, e hoʻomaʻemaʻe i ka mīkini, i mea e hōʻoia ai i ka kaʻawale.
Hoʻomalu ʻia ka pae wai e ka valve float, no laila ʻaʻole pono ka hana lima. ʻO ke kila kila piha ia, pēlā e hōʻoiaʻiʻo ai i ka maʻemaʻe o ka wai holoi.