Editor’s Note: A recent poll taken on NorthwestRVing.com indicates a good percentage of readers would like more tips and maintenance ideas. We appreciate your feedback and will include more tips and maintenance ideas starting with this and future entries.

Pages have been written about the cleaning and maintaining of your black tank (sewer) along with controlling odor, but the proper method to operate your gray tank is hardly ever mentioned. Following are some tips that will likely keep the area around your campsite smelling better (especially with the hot weather we have been experiencing in the Northwest) while making your tank dumping process more efficient.

You have settled into a full hookup RV space, hooked up the water, plugged into shore power and connected the sewer hose between the RV and the campsite sewer port. Seasoned RVers know you leave the black dump valve closed until you are ready to dump the black tank to avoid the “pyramid of doom*”, 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 in the kitchen and bath without having to worry about filling up the gray tank. However, unless precautions are taken, doing so will allow sewer gases to travel from the campgrounds sewer system, up through 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 neighboring RVers! 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, allowing gray water to completely fill the entire diameter of the hose in the lowest portion. The standing water in the hose 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 thus allowing 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 as shown in the photo. If not, running your hose up and over a couple of blocks, higher than the diameter of your sewer hose is sufficient.

Form a P-Trap when leaving the gray tank valve open

Additional tip: A day or two before you leave the campground, close the gray valve and straighten your sewer hose to remove the trap or place a Slunky or similar device that supports and slopes your sewer hose from the RV termination fitting to the campground’s sewer opening. When you are ready to break camp, dump your black tank first and then flush your sewer hose by releasing the captured gray water. The large rush of gray water will easily flush out any solids that may have collected in the low spots while the trap was in place. Typically the rush of gray water is sufficient to flush your sewer hose clean eliminating the need to further flush it with water from a garden hose saving time and water.

Hose should be supported when dumping the black tank

*The pyramid of doom occurs when you leave the black tank dump valve open while hooked to sewer allowing the liquids to drain from the black tank while the solid waste forms a pyramid below the toilet.

Dave Helgeson
Author: Dave HelgesonEmail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Dave Helgeson is the MHRV Show Director. He and his wife love to travel across the west in their RV. Dave writes about all things RVing but loves to share destinations and boondocking advice.


0 #1 Steve 2018-08-31 16:40
The visual image of the pyramid of doom is a bit graphic, but I guarantee I will not forget the advice, nor forget and leave the black water tank open. I am new to RVing, so this type of information is great.

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