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Do You Keep Your RV Gray Tank Open? Closed? How About BOTH?!

Do You Keep Your RV Gray Tank Open? Closed? How About BOTH?!

Leaving your RV’s gray valve open when fully hooked up allows you to take long showers without worrying about dumping or filling up the gray tank. But what about sewer smells that can come up from the campground sewer system? Here’s how to get the best of both worlds!

One of the luxuries of staying in a full-hook-up campground is the ability to use water freely for showers, cooking and washing dishes. The sewer connection allows you to leave your RV’s gray valve open, so water can run right out instead of filling up your gray tank.

Of course the black valve can NEVER be left open, since “solids” will build up in the black holding tank when the “liquids” run out. But there’s a fair amount of discussion about the gray valve. Some people recommend that you should never leave the gray valve open either, as it can allow odors from the park’s sewer system up into your RV.

Of course leaving the valve closed means having to pay attention to the water level in the gray tank, and dumping it every few days. Seems like a shame to have to do that when your RV is connected to a sewer line, especially when you’re staying in a full hook-up site for an extended period of time.

Since the drains under every sink and shower in an RV are equipped with a p-trap, leaving the gray valve open shouldn’t allow odors into the RV. The water in the traps blocks odors from entering the RV’s living space. Long periods without use can allow the water in the traps to evaporate, and driving on twisty or bumpy roads can cause it to slosh out. But both of these situations are easily remedied by running a small amount of water down each drain.

There is, however, a pipe with a direct connection to the sewer hose…. leading to the tank vents on the roof of the RV. This can allow air from the sewer system to come up through the roof vents. If you’ve ever smelled sewer odors in a full hook-up campground, it’s possible that someone’s RV is venting the park’s sewer system out through their roof.

In a recent RV Travel newsletter, we read about the simplest way imaginable to enjoy the luxury of a full hook-up RV park. You can leave your gray valve in the open position so water runs right down the drain. You don’t have to pay any attention to how full your gray tank is and you don’t have to dump it every few days. But there’s no chance for sewer odors to escape either. It’s the best of both worlds.

Watch the video to see how we did it!

Please use your full hook-up powers responsibly and don’t waste water! And be sure you know the answer to the question: Can You Dump RV Gray Water On the Ground Legally?


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PS….

Just a brief follow-up… Although this wasn’t a video about tank dumping, it is related, and there were some comments and questions about it. If the gray valve is left open, there isn’t any gray water available to flush the sewer hose after dumping the black tank. Here’s how we handle that.

Conserving water and monitoring tank levels are just part of life for most RVers, so it’s a luxury to be able to forget about it once in a while. When we’re in a full hook-up RV park for an extended stay, leaving the gray valve open allows us to take longer showers, while completely ignoring the level in the gray tank. We just use the trick we demonstrated in the video to prevent sewer odors from coming in through the open gray valve.

Then all we need to do is keep an occasional eye on the black tank level. Since we often take the load (sorry) off the black tank by making periodic use of the park’s bathrooms (as long as they’re clean), it takes a solid (sorry again lol) two weeks or more to fill it up. When it shows 3/4 full, we close the gray valve for a day or two, allowing gray water to accumulate in the tank.

When we’re ready to dump, we take a few seconds to put the entire sewer hose back up on the sewer hose support, then dump both tanks, black first of course. Plenty of water has now accumulated in the gray tank, allowing us to flush the sewer hose after dumping the black tank. When we stay in one place for an extended period, we appreciate being able to completely ignore both tanks for two-plus weeks at a time. This way of managing our tanks allows us to do that.

This is a perfectly fine way to handle shorter stays too. After boondocking for extended periods, we’ll sometimes treat ourselves to the luxury of full hook-ups for a week or so, leaving the gray valve open and using the same sewer hose technique. We simply close the gray valve a day or two before we’ll be leaving the park, and dump both tanks on the morning of our departure.

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Tonya

Saturday 9th of July 2022

Why is my grey tank 1 getting full when I valve open all the time cuz it's parked

Lea

Wednesday 12th of May 2021

Hi there! My husband and I are new to the full time rv life. My husband is a nurse so a lot of the rv stuff is up to me. We are currently hooked up for the season until October, and I already show that my one grey tank (shower and bathroom sink) is 1/3 full but we have it open to auto drain. If I am not moving the rv how do I go about cleaning the grey tanks? Thank you!!!

TheRVgeeks

Wednesday 12th of May 2021

Hi Lea! Even though you're sitting in one spot, you can try this: https://www.thervgeeks.com/gray-tank-sensor-cleaning/ Even without moving the RV, this can help.

Steve Sparks

Saturday 10th of October 2020

Anybody that's ever opened a sewer cap has seen roaches and other bug hiding inside the cap, leaving the gray water open is an invitation to having bugs and other creatures crawling up your drain! I'll be keeping mine closed!

TheRVgeeks

Saturday 10th of October 2020

Hi Steve! Keeping the valve closed is definitely a viable option, and guaranteed to block any type of bug from crawling in. But just for the record, we've never seen bugs under the sewer cap in over 17 years of full-timing. Maybe we're not going to the right places! LOL

Destiney

Thursday 2nd of May 2019

I been living in this trailer for almost a year the sewer system of the whole trailer park is mess up so every time is clog up the sewer water come back up on my bathtub is discussing but when I do call the land lord she said is not her problems now what I do

TheRVgeeks

Thursday 2nd of May 2019

Sorry to hear. Obviously your park has major sewage issues. We would suggest that until they fix the problem, you keep you gray valve closed to prevent the sewage from backing up into the trailer. Hopefully when you go to dump it each day, it won't come up instead of going down.

Elena Britt

Friday 12th of January 2018

Hello we have been living in our trailer for a year now and was wondering if we can leave our toilet tank open.... We don't travel it's our home. thank you .

TheRVgeeks

Friday 12th of January 2018

Hi Elena! Definitely not! If you leave the black tank valve open, the “liquids” will run out and the “solids” will pile up, dry out, and harden into a smelly mass. That’s commonly referred to as “pyramiding” and it’s a horrific mistake to allow that to happen.

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