Friday, June 9, 2023


Holding tank tips for the stationary RV

By Russ and Tiña De Maris
While the term “recreational vehicle” fosters visions of hitting the open road and exploring new sights, new civilizations, we don’t always boldly go where we haven’t gone before. Sometimes we may be “stuck” in the same place for a couple of weeks – even months. Having a “stationary RV” means special care of the black water holding tank.

smell-747First, NEVER leave your black water holding tank dump valves OPEN. Yes, you are hooked up to a sewer line, but getting all those nasty solids out of your holding tank requires the movement of a large amount of fluid. More than one RVer has learned the hard way that leaving the black water dump valve open translates quickly into a holding tank that won’t dump.

RV’s motion keeps black tank stirred up

When an RV rolls down the highway, it’s not just beneficial for us behind the windshield, seeing those new sights. Down under in the holding tank, that rock-and-roll motion of the rig keeps the black water tank stirred up. This contributes to the breakdown of solids and the removal of foul odors. Park your rig and don’t move it for a few days, a different setup occurs in the holding tank. Solids tend to gravitate to the bottom of the tank and an ugly sort of transformation begins to occur. We’ll spare you the grosser details, but it needs to be said that a goop-like substance can begin to coat the bottom of your holding tank.

That goopy coating is hard to get out of the tank and if not evicted can begin to build up and up and can eventually cause a blockage. To keep this from happening, when you dump your black water tank (which should be done ONLY when the tank is at least three-quarters full), allow plenty of time for the contents to evacuate.

Clear sewer hose adapter helps

Here’s where having a clear plastic sewer hose-to-dump port adapter is a good thing to have. When you dump the black tank you can closely observe just what’s coming out of the tank. After sitting for a number of days you may be surprised just how s-l-o-w-l-y those contents can be about coming out of the tank. Slamming the holding tank valve shut before the contents are clear can not only leave you holding more gunk in the tank, the stuff can also prevent a water-tight seal on your black water valve – not a good thing.

If you find the tank just doesn’t seem to want to “get empty,” then leave the valve open and have a helper run the toilet until the tank runs clear. We’ve found it may require a greater volume of water than the toilet itself will readily provide. We have a secret weapon: Our shower hose will stretch far enough to blast water down the toilet, making the job much faster.

Hot weather adds to the smell of black tanks

In hot weather, stationary RVers face another problem: sour tanks. The combination of heat and lack of motion can cause the breakdown of wastes in the tank to stop, causing a really, really stinky situation. Assuming that you are either not using any sort of holding tank treatment at all, or are using one that’s based on enzymes and/or bacteria, you may be able to clear up the problem by dumping a half-cup of baking soda down the toilet with a couple of gallons of water. This may “sweeten” an otherwise acidic condition, getting natural bacteria to begin waste breakdown, reducing the stink factor.

In really tough situations you may need to fill up the holding tank with water, dump it completely, and then add a couple of cups of baking soda and fill it up with water again. This time don’t dump the tank immediately; let the tank sit overnight, then dump it and “restart” the system with the addition of a bacterial and/or enzyme-based holding tank treatment. We had this happen once during a hot spring stay on the Arizona desert. The stench was overpowering, but the “fill, dump, refill with soda water, dump again” procedure proved a life (and nose) saver.


We tested tons of black tank treatments – this is the only one that worked



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6 months ago

They must have taken down the link to
in the list of recommended links above. Too bad, it may have been a good source.

RV Staff
6 months ago
Reply to  Ray

Hi, Ray. That link is still there, as far as I can see. That’s Dustin Simpson, and we highly recommend him, his advice, and his shop, California RV Specialists! Have a great day. 😀 –Diane

Debra L Goodnoh
1 year ago

What can I do to empty black water while permanent situation can you dump into a large above holding tank such as 100 gallon tank

1 year ago

Read (or heard) somewhere to empty the tank, throw a bag of ice cubes down the toilet, and drive on a bumpy road. The cubes supposedly rattle around & loosen the sludge. True?

1 year ago

For everyone who believe that motion (driving around) helps with dislodging and agitation- it doesn’t. Just look up the videos that Fit Rv has done and take a look. Best advice is to add a flusher and use it every 10 days or so with lots of water.

Ron Lane
1 year ago

Our coach sets from mid May through the first of October. By installing a 3rd gate at the bottom of the Y (just in fromt of the clear connector) I will use my soapy gray tank water to flush out the black tank once the black tank has been emptied. Works like a charm and keeps the black tank free and clean of the “goop” and totally eliminates odors and faulty sensor readings. When traveling and starting with an empty tank, I will add about 5 gallons of clean water along with a cup full of liquid laundry detergent and a cap full of Calgon water softener. I have not used an RV black tank additive chemical in 20 years or more.

Gary F Broughton
1 year ago

We sat all summer and I dumped on Sundays. Make sure you use lots of water when flushing the toilet. I then use the flusher for several minutes and observe the flutes coming out. I leave flusher going for a minute then dump the gray water tank. Never had a problem.

1 year ago

That’s why I’m glad RV designer installed a macerator. Relative quick and easy. There are portable systems and they also work well. I do carry a stinky slinky, but have never had to use it.

Jesse Crouse
1 year ago

I use the Borax and Dawn mixture and have yet to smell anything over a 3 year time frame. Works well on the Grey side too.

Michael Roach
1 year ago

Thanks for the baking soda tip ! I’m a long time Rver but that’s a new one on me .

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