Saturday, December 10, 2022


Why to keep your RV’s gray tank closed when hooked up


RV waste management expert Doug Swarts of explains why RVers should not only keep their black (sewer) tanks closed when hooked up in campgrounds, but their gray water tanks as well. Open both tanks to dump when they’re two-thirds full, but do not keep either open until then. You’ll be surprised to learn why the gray tanks (sink and shower) should be kept closed until it’s time to dump.

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2 years ago

Thank you so much for the great info!

Larry Byers
2 years ago

Thanks for the great information. I do have a question, we use a mixture of Borax, Dawn detergent and Calgon in our toilet after we dump our black tank. Is there something similar we should use in our grey tanks after we dump it?

2 years ago
Reply to  Larry Byers

You can use the same mixture in your gray tank. I do the same, only I use a liquid laundry detergent (Oxy-Clean) and Calgon in both my tanks every time we travel.

Tom Prevost
2 years ago

Ok that video might be one of the most enlightening I have seen on this subject. Im changing my procedures as a result. Thank you for all you and your team do to keep us informed b

Bruce F. Monte Sr
2 years ago

To those who leave their gray tank valve open to avoid flooding their rig, just make it routine to open it to drain MON, WED, Fri and you’re all set with the best of both worlds.

2 years ago

What about when you do laundry?

Les Brandt
5 years ago


I subscribe to your blog and read it every Saturday. You do a really good job with it!
Like any service, it is difficult to satisfy all the masses. I certainly understand the extra work it would take to provide a transcript on every video you do or have a link to in your blog. In the cases of videos, it would double. Not to mention, that the contributor would also have to provide a transcript.
While I empathize that not everyone can be in a position to get the bandwidth or afford the extra data requirements, there comes a point when you provide a service, that you just can’t be responsible for every need of every person.
I will reiterate that I think you do a great job of satisfying the majority!

edward stevens
5 years ago

I loved the article on the difference between 30 amp and 50 amp benefits. Is there a way I could speak to Mr. Mike Sokol or get in touch with him via a website or email? Thanks

Phil Atterbery
2 years ago
Reply to  edward stevens

Go to the RV Electrical FB page.

5 years ago

I used to do my grey tank the way he recommends in the video. After overflowing the grey tank and getting water damage in 5 out of my 7 RVs over 32 years, I started leaving my grey tank open.
One overflow is a big problem, and anything I can do to avoid another one is worth putting up with a few minor problems.
Yeah, and tank gauges don’t work any better when you keep the grey tank closed.
And P-Traps in an RV are the same as a P-Trap in a house, you need to pour some bleach down them occasionally to keep them smelling OK.

5 years ago
Reply to  Dave

Dave ,
You should have put an alarm in your shower pan as that is where gray water will overflow from your Gray tank first.
I would think the simple solution would be to dump your Gray water every 2 days or so to insure you don’t overfill your Gray tank. A simple 24 hour timer at your entrance door would also help serve as a reminder.
BTW — Pouring Bleach down your drains kills the bacteria you need to break down the waste in your holding tanks. –Doug (at)

5 years ago
Reply to  Doug

That’s why I chose a tub with a shower–so I can keep my grey tank valve closed until needed. It would overflow in my tub if the tank got too full. I know how many showere I can take before needing to empty as I find gauges are not reliable.

2 years ago
Reply to  Doug

Dave… your black tank is a temp holding tank, not a septic tank. There is no need to break down the waste as it shouldn’t be in there long enough for the bacteria to do anything.

Thomas R Sloan/ Alice M Sloan
2 years ago
Reply to  Dave

No Bleach!!

Sandy M
5 years ago

Chuck, some of us with limited internet would love to hear your advice. The request for a written copy of the video is easy to do. Just type it in under the video on the page that has the video, or post it as a comment. You are a writer and probably a fast typist, and probably already have a written script of the video anyway. We are just requesting a little help for us low bandwidth types. Should only take a few minutes of your time. This time of year, a lot of us are out in the boonies and have to pay to download a video. Just a request.

5 years ago

I bought a fifth wheel new, but the tank gauges are, at best, approximate. I can flush the black and the gauge works exactly once, then reads permanently full until flushed again. How can I figure out how long to leave grey tanks closed, with a washer to boot, when I simply cannot trust the tank gauges?

5 years ago
Reply to  Drew

First I would open the Gray tank when doing the clothes washing. The key to all this is to keep your Gray valve closed until the tank is 2/3rds full or thereabouts. Two people in an RV will get a feeling for how full the Gray tank is getting over time. The shower pan is where Gray water will surface first, and you can get a moisture sensing alarm, but I would get a 24 hour timer and dump the Gray when it goes off. –Doug (at)

Keira B
5 years ago

Both of my RVs have p traps in the sink drains. They are plumbed the same way as our house is. The only difference between my RV and my house is the addition of the holding tank and the hose that can be disconnected. If critters could come up the sewer line to an RV, and make it trough the P trap, they could also come up into your house the same way.
If anything it is more difficult for a bug or rodent to come up into an RV than a house. They would need to climb into the holding tank, then get to the pipe at the TOP of the tank before they could get to your sink drain. A rat small enough to make it up a 1.5 inch sink line would have a hard time jumping up over a foot to a hole in the roof of the grey tank. I wonder if a cricket or roach could make this journey.

5 years ago
Reply to  Keira B

We have not heard of any bug or critter or fly for that matter getting through the P-traps into the living space of the coach itself. WE have heard a number of times about things getting into the Gray holding tank. Sewer flyies get into the Gray tank then go up the vent and back down into the Black (if the coach has only 1 roof vent) tank. Now the flies can enter the coach when you open the toilet valve. In one case that happened to the wife and when the tank “sociologist” cleaned the black tank he saw a LOT of maggots! This convinced me that keeping the Gray tank closed is what we do—just sayin! –Doug (at)

Glenn Fidler
5 years ago

don’t have access to unlimited wifi. can not watch video, should have the story in written form so people can read it.

Toby pup
5 years ago
Reply to  Glenn Fidler

Agreed. And some of us do not have ultra fast connection. Written is better. Why wait all day to watch a “talking head.”

5 years ago
Reply to  Chuck Woodbury

Chuck, I don’t think anyone is saying don’t do videos (I like them) but requesting to add a transcript so those with low bandwidth can read the contents. With speech to text on almost everything now, it shouldn’t be too hard to do. Thanks.

Paula jones
5 years ago
Reply to  Chuck Woodbury

thanx for all you do….very appreciative here…

Tommy Molnar
5 years ago

Prior to watching this video, I’d never given much thought to this. We generally leave our grey tank open – UNTIL NOW. This makes perfect sense to me.

We would close our grey tank the day before we were going to leave a park so there would be water to wash out the hose after the black tank was emptied. We thought everything was cool. We’re smart RV’ers, or so we thought.

After 20+ years of RV’ing, I’m not averse to learning something new, especially concerning yukky black and grey tanks. We’ll be visiting the “RV Proctologist” when we hit Quartzsite in February.

Claude Denton
2 years ago
Reply to  Tommy Molnar

Hi all….
Re grey tank valve. My Newmar has a combo washer dryer that the water from it goes into the grey tank before it leaves the coach. If the valve is closed the tank will fill and keep on filling. Guess where it goes when the tank gets full? We found out the hard way.
It backed up into the shower and eventually out into the coach. Fortunately we were home at the time and didn’t create that much of a mess. So be sure and check how your coach washer is plumbed, and if it is,make sure the valve to the grey tank is open before you start a load of clothes or else. 😉