Most popup campers don't have holding tanks....so you're left with either portable containers or use 5/8 garden hose to drain off your grey water. The kitchen sink has never been a problem because of the height off the ground. The shower on the other hand is very slow draining unless you have perfect grade away from the camper. I got tired of a slow shower drain and came up with this.... A 500 gph automatic bilge pump in a 2.5 gal bucket plumbed to a fitting for my existing hose. Works like a champ.
Trying to upload pics but it keeps timing out on me......maybe later.