Our 1999 Starcraft Venture PUP did not have a holding tank either. It had a drain on the side of the trailer where you could hook up a garden hose. I took an old garden hose and cut a short section off it but left the end that attached to the camper. I then used a blue 6 gallon jug to catch the water. Ours did not have a shower, only a sink. I then took the jug to the nearest bathroom, pit toilet, or wherever, and emptied it. Funny, we still have the blue jug, and 6 more. I did mark that one for sink water and do occasionally use it catch "gray" water from various sources. The other 6 containers are used for fresh water, for extra water when camping and anticipated power outages at home (since we are on a well at home).
Notice the blue jug at the back end of the camper: