I purchased a fish table for my cargo van campouts, it has a sink/drain that can empty into a 5 gal HD bucket with lid adapted to the flex hose. I can place the bucket in a granny cart before filing it, & when it's full can wheel it into the bushes or to the dump station. The granny cart is rated for 150 lbs, the bucket neatly & securely into the cart & is low enough to fit the assembly under the table. I put a screen in the table drain to remove all food particles (they go in the waste bucket), using biodegradable soap that will not harm the flora & fauna, it can be dumped into a pre-dug hole. Table, cart & bucket cost less than $95 much cheaper than the $150+ grey tanks I looked at on Amazon. The hose can be set up so you even have a P-trap. I had to drill a hole in the lid to receive the hose & put a drain spigot near the bottom to drain it, Youtube is an amazing site! Everything folds & stores except the bucket but that fits on the bottom of my HD bucket stack (5).