Saturday, December 3, 2022


Cheap device prevents accidental RV sewer overflow


Doug Swarts ( and Chuck Woodbury of discuss how a simple, inexpensive device can save the day (as well as a lot of money on a major repair) when cleaning out an RV’s black (sewer) tank. A variety of the devices mentioned in the video are available for around $10 to $20 on Amazon.

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Forrest McClure
2 years ago

The San-T-Flush instructions say to leave your drain valve open while using it. Obviously, if you do that you will not overflow your black tank into the interior of your RV. That said, occasionally I’ve also used it the way Doug and Chuck describe.

2 years ago

I would think a better solution would be a gallon meter. You know how big your tank is. You set it to do that many gallons of water and when it measures that much it shuts off.
That way you know you are 3/4 full for sure. But i also agree with other people…i wouldnt want to TRUST a plastic device.

Sink Jaxon
2 years ago

On my rig, I have a little sign that says “Do not flush holding tank with valve closed”. So I always leave it open when flushing, which make sense to me. The sprayer rinses it out, and I watch til the water runs clean thru my clear elbow. Shut the water off, close the valve. But before I take off I put a couple toilet fulls in the tank along with a little enzyme. Seems to work for me.

2 years ago

The one thing they forgot to mention when he said to use your garden hose to Flush. WELLLLL, it should NOT be your Fresh Water Drinking Hose! Use a separate hose for Flushing the Black Tank Only.
These Flush systems on RV’s are prone to failure and can blow back into your hose once the water pressure is cut off. You Don’t want anything from the BLACK Tank getting into the hose.

Just my 3 cents worth.

Gene Cheatham
2 years ago
Reply to  Jeff

I put a back flow preventer on my dedicated black water hose too, even though some rv’s have one built in. They are available at any decent plumbing supply department/outlet.

5 years ago

I have used these hose timers in my garden. They are very prone to failure. One time it shuts off, and the next for some unexplained reason does not. I suggest you use a timer on your phone and consider the phone timer a first priority!

Steven M Jenkins
5 years ago

Could not find at Amazon the one shown in the video. All the others had significant number of bad reviews, saying they did not work (i.e. they did NOT shut off the water and led to flooding). So . . . I shall not order one. Thanks for the video anyway.

RV Staff(@rvstaff)
5 years ago

Thanks for writing, Steven. I just looked on Amazon (clicked on the link above the video) and saw several timers very similar to the one in the video. Near the top of the timers listed was “Amazon’s Choice,” which costs about $9, and had a 4.1-out-of-5-stars rating, with 819 reviews. Sounds to me like pretty good “insurance” for a very small investment. —Diane at

5 years ago

When parked I empty and flush my black tank once a week. After emptying I close the valve and add water for 5 to 8 minutes then empty and might rinse one more time. I have a clear plastic pipe at the RV end of the sewer hose to monitor when it’s clean. I use the stopwatch function on my wristwatch to monitor the time when adding water to flush. I can hear the water going in to flush the tank and if I go the 8 minutes the water has reached the sprayer nozzle as the running water sound stops. I like the above idea of using a programmable device to measure the number of gallons then I won’t have to worry about overflow anywhere in the system.

5 months ago
Reply to  George

I also use my phones timer, set to 6 minutes for a flush without issues. I just can’t bring myself to trust something that only cost about $10.00.

David Ozanne
5 years ago

I had a bad exp[experience with a black water flush that was not marked. I thought it was the fresh water input and hooked it up on my first trip in that MH. The toilet did not overflow but the water went all the way up the vent pipe and all over the place. A good Samaritan turned off the water for me and told me when I got back to the motor home. Never did it again.

5 years ago

I just use my watch or cell phone. With typical rv park water pressures it takes between 3 1/2 to 4 minutes to fill the tank with a hose…very easy. Nothing else to buy.

Bill T
2 years ago
Reply to  Drew

Hi Drew. How many gallons is your black tank?

2 years ago
Reply to  Bill T

Bill T,

44 gals. Water pressures can vary. I’ve found 3 minutes is max when the pressure is high (around 90), and closer to 4 minutes when it’s 70 or so.

Bill T
2 years ago
Reply to  Drew

Thanks Drew. I now have a base value to adjust for 32 gallons. Cheers.

2 years ago
Reply to  Bill T

WOW! Drew posted 3 yrs ago and answered your question pretty fast. Must have been waiting for someone to reply!

Stay cool

Robert Peterson
5 years ago

Wouldn’t it make sense to have a similar device that shut off after a given amount of gallons flowed through it. You know how many gallons your tank holds, so you could “program a number of gallons into it and get the level you want.

2 years ago

You can get the capacities of your rig on line. Also, be aware that most of these devices have some restriction- so you won’t be getting the desired pressure to do a good flushing.

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