Funny (to me) story. We only use the blue tote for grey water. After we came home from a 9-day trip, it had been hosed out after use, put back in the storage bin. While I was cleaning the TT in the driveway, I opened all the caps to let it air dry the inside. Set a small fan next to the dumping valve cap, and let air blow into for 2 hours. It just wasn't drying out inside and I couldn't figure out why, after I had stuck some paper towels down there to get the excess out. Finally 3 hours later I was packing back up and I realized I never opened the valve....I was blowing air into a closed valve. Duh....