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


RV waste management expert Doug Swarts of Drainmaster.com 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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Larry Byers

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?

Tom Prevost

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

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.

Les Brandt


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

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


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.

Sandy M

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.


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?

Keira B

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.

Glenn Fidler

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

Tommy Molnar

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.