Wednesday, September 28, 2022


Here’s how to keep your gray valve open without the stink

Editor’s note: In general, you should always keep your gray tank closed, opening it only to dump. In some circumstances, perhaps the technique below would be of use to you, but as a general rule, keep your gray tank closed in the campground or RV park.

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?

This should do the trick!

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.



Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Inline Feedbacks
View all comments
Mike Sherman
1 year ago

No biggie leaving the grey tank open if you never pour grease down the drain, use a strainer to capture any food particles and occasionally close the valve, pour chemical in, then flush when full.

2 years ago

First world problem . If you’re too lazy to manage your tanks, you probably shouldn’t be camping. Happy Trails.

Rory R
2 years ago

Well, I guess I took laziness to the next level. Once we are setup, hoses in place, both grey and black tanks valves are closed. I check the status of both tanks and when I need to dump, it is a simple push of a button and my tank(s) are dumped, then I close again, by clicking another button. I never have to go outside to dump a tank. After all there is more than sewer gases that can get into your tank system. bugs and rodents are a lot harder to get rid of than gases that smell. I thank the folks who designed a way to electronically control tank valves. I might be lazy, but I’m not cold, not rained on, because I don’t have to go outside to dump my tanks, regardless of the weather or time of day/night.

m Botts
1 year ago
Reply to  Rory R

would love to know, what that “button” setup is, and how difficult to get installed aftermarket?

2 years ago

It would be interesting to know how many of those that answered they keep the grey tank closed until it’s full stay for longer than 2 or more months. It would also be interesting to know how many have a washer on board.

And I agree with Lynn and Chuck in their observance of how lazy people are and “if the tank indicators worked as they should”.

Michael Mccracken
2 years ago

I have always heard that you should never leave your gray water valve open. Leaving it open causes a build up of grease and food particles in the tank. Your article seems to suggest leaving it open is ok?

2 years ago

We leave the grey tank open when we are using our washing machine, but that is the only time we leave it open. We do make a p trap at that time also to be sure stink doesn’t back up the line. When we drop our black tank I want as much water as I can get to flush and flow out the sewer hose. just sayin.

2 years ago

A certain campground in AZ would have your head for creating a trap. NO part of the slinky touches the ground. And they check!

2 years ago

RE: Grey tank. We count showers we take. After 4 showers, we know it’s time to empty before the shower will begin to backup.

2 years ago

Why not just keep the grey tank valve closed like the black tank and then dump when needed? Are people that lazy that they can’t monitor their tank levels then walk outside to take care of the deed. Or for the lazy ones there are 12 VDC Auto Dump Valves you can install then just flip a switch inside to dump.

John M
2 years ago
Reply to  Dr4Film

Agree 100% it only takes few minutes to dump, and how hard is it to push a button on your monitoring panel to check your tanks.

Chuck Dunn
2 years ago
Reply to  John M

If the level indicater worked the way it should, this would be great.

2 years ago
Reply to  Dr4Film

Yes, they are that lazy, that is why we have power awnings, omnidirectional antennas, power stabilizers and auto changeover regulators, all of which are troublesome.

2 years ago

We never leave the hose out,

Tony Grigg
2 years ago
Reply to  teubner

Just to be clear, are you saying that at ‘dump time’ you get out the hose, hook up, dump, flush, remove the hose and store it again until the tanks are full again? If so, why do you do it that way? Curious here.

2 years ago

A good way to stop any significant solids from entering your gray tank is to use those inexpensive little mesh strainers that set in the sink & shower drains to capture any solids. We have a much cleaner gray tank since we started using these strainers a few years ago.

Chuck Dunn
2 years ago
Reply to  Fred

They don’t stop grease.

2 years ago
Reply to  Chuck Dunn

I hope you’re not putting grease in your sink or tanks.

2 years ago

As long as you are aware that any solids that flow into the gray tank will settle at the bottom as the liquid flows out. We keep our gray tank valve closed for the same reason we keep our black tank valve closed; to prevent solid from settling and drying in the bottom of the tank.

Sign up for the RVtravel Newsletter

Your information will *never* be shared or sold to a 3rd party.

Subscribe to our newsletter

Every Saturday and Sunday morning. Serving RVers for more than 20 years.