Thank you all so much! I have taken all of this into account, and we spent this past weekend using the camper for the second time. I know the grey was empty upon set up, and the kitchen drain worked perfectly. I was extremely cognisant of my water usage in the kitchen, and we opted to shower in the campground bathhouse. On Saturday evening, the kitchen drain slowed WAY down, and then quit draining altogether. Upon inspection, the tub had a small amount of water collecting right at the plug. Hubby went out and opened the grey valve and released a good amount into a large container, and the water drained properly. Seeing the water almost fill a 22 gal container, its easy to understand that 15 gal grey is just really REALLY small. I think we're good as long as we can keep a bucket or bin handy for a quick release during our trips. So far, we're on a 2 night weekend only schedule, so its not as inconvenient as it sounds.