Grey Wolf 26DBH Holding Tanks … As most of you know travel trailers usually have three holding tanks: fresh water, grey water, and black water. Fresh Water - The 26DBH fresh water tank holds 46 gallons and is used when you don’t have city water hook-ups. One gallon of water weighs approximately 8 pounds, something to consider when you are concerned about total weight of your RV. When full the 26DBH fresh water tank holds about 368 pounds of water. I only keep about 5 gallons of water in my fresh water tank mainly for flushing the toilet for travel stops. I suggest you run the fresh water tank near full or near empty. The fresh water tank does not have baffles to stop liquid surge so a partially filled tank allows the water to move back and forth and could cause trailer sway. There are plenty of good articles on the internet about how to keep this tank sanitized. Grey Water – The 26DBH grey water holds 38 gallons of water ...