By Dave Helgeson
You have settled into a full-hookup campsite, hooked up the water, plugged in the power and connected the sewer hose between the RV and the campsite sewer inlet. Seasoned RVers know you leave the black dump valve closed until you are ready to dump the black tank, but what about the gray valve?
Many RVers like to leave the gray valve open so they can liberally use the shower and run sink water without having to worry about filling up the gray tank. However, doing so will allow sewer gases to travel from the sewer system up your sewer hose and out the gray tank plumbing vent located on the roof of your RV. While it is unlikely you will smell the offending gases from inside your RV, it is very likely anyone in the vicinity of your RV will. Not the best first impression to make with your fellow campers!
One solution is to leave the gray valve closed until you need to dump the gray tank and then close it again. This can become tiresome if you are camped in the same location for weeks or months on end. The best solution is to arrange your sewer hose so it forms a P-trap. The standing water in the trap will prevent sewer gases from traveling up your sewer hose into your gray tank, but still allow gray water to freely pass down the sewer inlet. This allows you to keep your gray valve open without being an odiferous offender to your neighbors. Many times the campground sewer hookup is elevated off the ground, providing an automatic trap for those that leave their sewer hose on the ground. If not, running your hose up and over a couple of blocks, higher that the diameter of your sewer hose, is sufficient.
Final note: A day or two before you leave camp, close the gray valve and straighten your sewer hose to remove the trap or place your Slunky sewer hose support under the hose. When you are ready to break camp, dump your black tank and then flush your sewer hose by releasing the captured gray water. This rush of gray water will easily flush out any solids that may have collected in the low spots while the trap was in place.