Holding tanks March 10, 2001, 01:27:42 pm Yahoo Message Number: 2565My 86 22' RL has 20 gal blk. water and 20 gal. grey water as standard. I installed an extra 20 gal. grey tank. It is situated at thed rear of the rig up against the floor. There is a pipe that connects to the std. tank. when the std. tank is full, the water then backs up into the spare tank. When dumping all the water is drained from both tanks. A vent is required on the spare tank. We are well satisfied with this arrangement