Well, your not alone!
By Cliff Maurand
I have heard many stories from various pop-up campers about how their sink won't drain properly. And having experienced this first hand for myself, I know where they are coming from. On several occasions, I had a long garden hose attached to the sink drain outlet on the side of my Starcraft, and it fed directly to an in-line sewer hook-up, complete with small hose attachment hardware.
And from that point on, I spent the rest of the weekend trying to figure out why I kept finding standing water in the sink. I'd go out and check the hose for kinks, and none were ever found. However, when "fiddling" with the hose, I could hear it start to go, all of a sudden, the tell tale sound of the swish as it went. Several more times during that and a subsequent weekend, I went through that drill. Each time I thought it was the placement of the drain hose, and each time I thought it was fixed, it would stop draining again.
After watching the next door neighbor going through the exact same drill on his pop-up, which was a brand new unit compared to my 20 something trailer, I knew there was something more to it than just the placement of the hose. We studied the problem, but never really came up with a solution that weekend. I wound up cutting the hose down to a 3 foot section, and feeding it into a gray water tank, and did the hand dump 2 or 3 times per day.
After we returned home from that trip, I did some searching, and found out we were not alone with the problem. Two of my best places for information come from the web. The news groups or usenet (alt.rv.pop-up-trailers) gave me my first indication that there was a way to fix the problem. Subsequent searches at the Pop-up Times message boards also provided a wealth of information.
What I discovered were an array of different reasons why this would happen, and a sampling of different home made devices designed to "fix" the problem. The most re-occurring theory centered on the lack of a vent system in the drain on a pop-up. Others had sited the small size of the hose, and trapped air bubbles, all of which I discovered played a part in the problem. To further my knowledge of the way these things should work, I went on another discovery trip, this time to the RV dealers in my area.
Knowing full well that every house has a vent in place on it's plumbing system, generally a small pipe protruding through the roof near the bath rooms and kitchen. These are known in the area I live in by the construction crews as "the stink pipe." With that in mind, I looked at how the hard sided units were plumbed, and discovered that every single one of them, had some kind of vent tied into the plumbing.
Though they didn't go through the roof, they did vent to the outside of the unit. From the bottom of the sink, and at the wall, the drain pipe would run into a "TEE", with one end heading down toward the system outlet or built in grey water tanks, the other end rising up the wall, and exiting the trailer at a point level with the top of the sink. There was a small cover with an opening on it for aesthetics.
With that in mind, I sent my observations to my friend John (with the newer pop-up). I sent him pictures, story links, and my observations. He took all this information, looked at all the pictures, and headed for the hardware store. Trying to avoid garden hoses, and non-fixed attachments, he designed a system that can be assembled on-site in a matter of seconds, fit's snuggly and securely to the camper, and has fittings that will accept a standard garden hose for the drain.
His pop-up drain was located underneath his trailer, which made placement a little difficult. With his design, he could simply screw the attachment onto the drain outlet, then place the pipe parts together by "press fitting" them. Attaching a garden hose to the other end, we tested this device, and it worked great! The drain that comes out underneath the trailer is low to the ground, and the vent tube had to rise to top of the sink level in order to work properly.
We tested it at various lengths, but found as long as the vent would extend to the level of the counter top where the sink was located, it drained just fine, each and every time. We had our cure for the problem! It works great, and cost little to make.
We also understand that not everyone has the patience or manual dexterity to build these things, and have decided to offer them for sale to the public. If you are interested in purchasing one of these, just email the webmaster for more information. The cost is $25 plus shipping & handling.