325 Gallon Open Top Cylindrical Tank A-OP0325-36, 325 Gallon Open Top Cylindrical Tank. This tank is often referred to as an open top vertical batch tank. This tank is designed for indoor usage and as the name suggests is most often utilized for batch chemical and mixer mount applications. The Ace Open Top 325 gallon tank comes standard with a bolt on lid and a 2" bulkhead drain fitting. The tank is manufactured of medium density polyethylene and is a rated with a specific gravity of 2.0.