I contacted Ryan at Bulk Reef Supply. He's convinced the membrane isn't seating right. My DI canisters have always run out that quickly so I never had a point of reference to how quickly it should be running out. I'm glad Chubakah started this thread. Sorry for the hijack! Thanks to everyone for bringing that to my attention. I will be testing my post RO water a lot more in the future. Pat_13, where in WV do you live? Half of my family is in Ranson, Charles Town, and Kearneysville. If I can ever help you with anything or would like to combine shipping on any future orders, shoot me a pm.