AquaCera CeraGrav LP5 Gravity Water Filter System - Empty Housing Only - No Filters The CeraGrav is a durable water filtration system &#44; made from high density polyethylene.. The LP5 is the perfect water filter system for camping and hikers. CeraGrav is highly durable&#44; The Doulton Gravity water systems hold up to 5 Imperial or Slimline Doulton ceramic filter FDA approved material. The Gravity LP5 does NOT require power! Gravity is used to filter the water through the filters.