Friday, December 1, 2023


Do you keep your gray tank open or closed when hooked up?

When you have full hookups, do you normally leave the valve to your gray water holding tank (sink and shower water) open? Or do you keep it closed until the tank is full or nearly full, then open the valve to dump?

That’s what inquiring minds want to know this week! Just click your answer and the current tally of responses will then instantly appear.

Poll may take a few seconds to load.

Chuck Woodbury
Chuck Woodbury
I'm the founder and publisher of I've been a writer and publisher for most of my adult life, and spent a total of at least a half-dozen years of that time traveling the USA and Canada in a motorhome.



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Dwayne (@guest_113901)
2 years ago

Just used rv for the first time. The night before leaving I realized i hooked the sewer but didn’t open the valve. So glad I forgot after reading post. This is going to be a learning experience 😳

Nancy (@guest_16279)
6 years ago

At an RV Park we visited in NH, we heard that, due to a malfunction, sewage backed up inside a motorhome that had left their grey tank open. It was totally destroyed.

Larry Lee (@guest_16196)
6 years ago

Great comments! Lesson learned. I am converted from “mostly open” to “always closed”.

Bob (@guest_16004)
6 years ago

I leave the gray valve open except for the night before dumping the black tank. I have flushing nozzles in both tanks that are installed in my water system with back flow preventers, on/off valves, and switching valve to go from one tank to another. Have had this system for 15 plus years with zero problems and its easy to use with no additional hookup.

K4kev (@guest_15992)
6 years ago

I left mine open once many years ago and had a roach and other insect infestation as a result. Never again! The valves stay closed until time to dump.

rvgrandma (@guest_15965)
6 years ago

During spring, summer and fall the gray is closed. During winter when it is going to be freezing at night I leave it open because I always have water running at night.

Plus, nothing worse than having your gray water frozen shut. Black water you can get by on if it freezes and a hair dryer won’t thaw it by walking to the rest rooms.

Doug (@guest_15940)
6 years ago

Great comments on a very controversial subject. After full timing for 10 years and working in RV Waste Management talking with hundreds of RVers on this subject, my humble opinion is to always leave your Gray valves closed until the tank is 2/3rds full.
Drew is correct, leaving any tank valve open upsets the RV park’s air balance which can cause odors in the park, especially when someone in an adjacent row dumps their tanks. The air takes the path of least resistance, not necessarily out the Park vent, which it would if all the sewer inlets in the park were closed.
BrucinAZ is also spot on. Critters of all kinds are in the sewer system, both septic and city systems, from Sewer Flies to Sewer Rats! Stories shared by customers over the years are plentiful enough to swear me off of ever leaving my valves open all the time.
In addition, leaving your Gray tank open allows food particles, grease, toothpaste, shampoo etc. to lay in your tanks and accumulate. Remove your galley sink P trap or bathroom and disturb the black gunk in it and smell, that should cure you as this is what the inside of your Gray tank is like. Keeping the valve closed especially if you have 3″ valves on your Gray tank will help flush out most of this as the water creates a vortex in the middle of the water sucking most of the scum and particulate out and down the drain.
The exception would be to open the Gray valve when using the washing machine or showering then close the valve.
The process to having an uneventful dumping experience over time is very simple.
1. Keep the tank valves Closed until ready to dump, exception noted above.
2. Use plenty of water in your Black tank and NEVER leave it Open, unless dumping.
3. Always travel with a couple of gallons of water in your tanks as the agitation helps keep the sidewalls cleaner.
If you want more information contact us 877 787 8833 Toll Free.

Mel Goddard (@guest_15955)
6 years ago
Reply to  Doug


Pat (@guest_15932)
6 years ago

I have always read that you leave both valves closed until you are ready to dump. Black first, gray rinses out the hose. Rinse black tank with fresh water, then drain gray. If you leave gray open, you will have to rinse your hose with fresh water only. Rinse with fresh after draining gray water for a cleaner stinky slinky.

Drew (@guest_15928)
6 years ago

Those of you leaving valves open are helping to contribute to the stink you sometimes experience in rv parks. The campground sewer system can find a vent through your open gate valve and send a stench up your vent stack and out in the park. I know people don’t do this on purpose but those are the consequences. The reason some think you can’t leave the valve closed with the washer is it can use a lot of water- therefore the possibility of overflow…just watch your tank levels and dump before you do the wash. I’ve heard the claim that critters find their way into your tanks but I’ve never actually heard of it happening…anything is possible but some things are more likely to happen than others.

Diane M (@guest_15910)
6 years ago

Surprised by the poll. Like long showers so leave gray open until a day or two before leaving. Then shower to fill tank. This gives a full gray tank to flush out the black after dumping black first. If it’s just an overnight stay leave everything closed up. We’ve traveled over 300,00 miles in 20+ yrs. Never had a problem.

Bill (@guest_15893)
6 years ago

Our washer/dryer manual says not to operate it with valve closed. I normally keep the grey valve open except when preparing to dump the black tank, and have never had a problem. But then, we move often enough and dry camp often enough that we get the grey tank full every month or so.

By the way, as a sanitary engineer I spent a lot of time looking in sewers. I rarely saw any critters, a few roaches now and then at most, but I was on the east coast so the water may attract more wildlife out west.

Dick and Sandy near Buffalo, NY (@guest_15885)
6 years ago

We can not agree more with the comment by BruceinAZ. Even with having to empty out our gray tank more frequently with using our stacked washer/dryer, our gray and black tank valves are closed until they require emptying. No odors, no critters, no problems.

Bob (@guest_15884)
6 years ago

We open ours when we are operating the washing machine which is weekly and coincides with a preceding black tank dump.

hank hoyt (@guest_15858)
6 years ago

Howdy, I have 2 gray tanks Galley and Head. Head stays closed till I dump Black but Galley stays open.

Mike (@guest_15848)
6 years ago

I just open the gray after a few long showers then close it up until time to flush black tank before I depart…

Triker (@guest_15846)
6 years ago

I have it open all the time until 2 days before I need to dump the black tank. Then it is closed until after the black tank is dumped. Then it is open until 2 days before the black tank needs dumped.

Gerry (@guest_15871)
6 years ago
Reply to  Triker

Agreed, works fine.

Judy G (@guest_15836)
6 years ago

I’m in a Class C with no ‘toad’. When headed to town or to travel, I can dump and flush and then stow the sewer equipment fairly quickly.

BruceinAZ (@guest_15770)
6 years ago

Leaving the gray water valve open is just begging for trouble. There have been some real horror stories of varmints, vile insects, snakes and other undesirables taking up residence in grey water tanks and even getting further inside RV plumbing and sinks/showers. You probably don’t even want to know just what kind of critters live in sewer/septic systems. Besides, the more gray water you have to run through your hose after emptying the black water tank the better. Other than pure laziness there is no reason for not minding tank levels and emptying only when necessary or when breaking camp.

Terry (@guest_16404)
6 years ago
Reply to  BruceinAZ

The sewer line is the issue, not which tank you are leaving open…and yes, even leaving it open just 1 time for a night can–and did— result in sewer bugs climbing on the walls, fridge, tv…all in different areas of the rig Never again! Even if there were backflow protectors.

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