NOTE: When camping at a full hookups campground, it is common to have your RV connected to the campground sewer system for the duration of your stay. A point of clarification: Most often, campgrounds are on septic systems due to their distance from a typical city sewer system. In this article, we will refer to any campground system as a “sewer system” even though it may be city sewer or a septic system. For you, the RVer, the distinction isn’t important.

Black valve in the closed position on an RV
Black valve in the closed position

At Unique Camping + Marine, we always recommend keeping your black water holding tank valve closed (except while dumping the black tank).

We also recommend keeping your gray water holding tank valve in the open position while at full hookups campgrounds. This practice will allow your black water holding tank to function as designed and will allow gray water to drain out of the RV whenever that system/plumbing is used. For more information on this (sometimes controversial) topic of gray tank valves, read this article. This is all well and good until you start getting sewer gas from the sewer system backing up into your RV through your sinks and showers (because the gray tank valve is open)! Not only do these sewer gasses stink, but they can also be dangerous, so it is important you prevent them from entering your RV. Luckily it’s a very easy fix! 

 

P trap under an RV bath tub
P trap under an RV bath tub
HepVo style drain trap under an RV bathroom sink
HepVo style drain trap under an RV bathroom sink

Most RV sinks and showers are equipped with either a P-trap or a HepVo valve style trap, which are designed to keep these gasses and odors at bay. However, sometimes these do not do enough to stop the sewer gas from making its way into the RV.

Sewer discharge hose setup in a p trap with water in it to stop sewer odors from entering the RV at a full hookups campground
Sewer discharge hose setup in a p trap with water in it to stop sewer odors

Because of this, we recommend placing a simple and easy P-trap in your sewer discharge hose. Setting your hose up in this manner and adding some water to the P-trap will provide a vapor barrier between your RV and the sewer system so it remains sewer gas free. 

Sewer discharge hose on a sewer support connected to an RV discharge manifold and running to the sewer discharge port
Sewer discharge hose on a sewer support

In order to set up this easy and effective P-trap, you will need a discharge hose support to keep the hose off the ground. In fact, this device is required by many campgrounds, so you should have one on-hand at all times. 

Sewer discharge hose connected to the discharge manifold and forming a p trap with a low point before the sewer hose support from an RV
Sewer discharge hose connected to the discharge manifold and forming a p trap with a low point before the sewer hose support

After you have connected the hose  to your RV discharge port, allow the sewer hose to fall below the high portion of the sewer hose support (almost let it touch the ground). Then the hose will loop back up and rest on the sewer support. If your hose does not stay in the position you would like it to, use zip ties to hold it in place. 

Once the P-trap has been added to the sewer hose, make sure that the black water holding tank valve is in the closed position.

A hand opening the gray water valve once the p trap has been setup at a full hookups campground
Opening the gray water valve once the p trap has been setup

Open the gray water holding tank valve to allow the water that was in the tank to fill the P-trap with water. This will act as the vapor barrier. If the gray water holding tank is empty when you set up the hose, don’t worry!

RV kitchen sink running for 30 seconds to add water to the p trap
RV kitchen sink running for 30 seconds to add water to the p trap

With the gray water valve open, simply run some water at one of the sinks for about 30 seconds. This will allow water to flow through the plumbing system and gray water holding tank, filling the P-trap with water. 

Having a P-trap in your sewer discharge hose, with water in the P, will give you an extra layer of protection in the fight for an odor-free RV and a worry-free camping trip.

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