We’re sure that you’ve heard the advice at one time or another from “experienced” RVers that you should dump a bag of ice into your RV’s black tank to scrub it out or knock things loose. When you think about it, it sort of makes sense: The ice cubes are fairly large, they tend to have hard edges, they’re solid and melt slowly, and any sort of agitation from driving your RV around has to produce some sort of scrubbing action, right?

Our answer: Sort of, but not really. Here’s why:

Geometry is against you

A ten-pound bag of ice contains 8.75 quarts of cubed ice. That’s a third of a cubic foot of volume or 576 cubic inches.

The typical RV black tank is anywhere from 30 gallons to 50 gallons in capacity. Some are more cube-shaped, like in a motorhome, while others tend to be flat and pretty long. That 30-gallon tank is 8,333 cubic inches of volume, while the 50-gallon tank is 13,870 cubic inches. 

If you put one 10-gallon bag of ice down your toilet into your black tank, and the tank is 30 gallons in capacity, that ice takes up 7% of the volume. To get to even one-third capacity, you’ll need to pour five, 10-gallon bags of ice down your toilet.

If you have a motorhome or fifth wheel RV with a bigger tank, say 50 gallons, that one bag of ice is just 4% of the tank volume. Getting the tank full to one-third capacity would require over eight 10-gallon bags of ice. 

Even with that volume, there’s no guarantee that the ice would work, because….

You have to drive like a mad man

Actual tests done with transparent holding tanks mounted in the back of pick up trucks and observed remotely with cameras showed that ice in the tank barely moved around unless the driver literally drove erratically, cornered at unsafe speeds, and over the roughest of roads and obstacles such as curbs and drops.

None of the conditions in the tests was anything that any RV owner would subject their RV, tow vehicle, or motorcoach to without suffering severe suspension and tire damage.

So add in some water for better movement

You want the ice moving around, but not floating, so add some water. Sounds like the right next step, right? The problem is, only the ice on the top of the water is now floating and causing any possible agitation to the sides of the tank. The ice below the surface of the water is just soaking…and melting. 

And who’s to say what the correct water-to-ice ratio is correct unless you have some sort of elaborate camera and lighting system set up inside the tank. In the end….

Ice just isn’t that abrasive

Scrubbing works by abrasion, but an ice-and-water mixture is a low-friction situation. The ice just doesn’t collide with anything with a great enough force. Most of the time, stuck-on waste is pushing the ice away from the surfaces.

In the end

Most owner-initiated cleaning action inside holding tanks comes from the volume of liquid, namely clean water, rather than any sort of additive that you are putting into the tank. In fact, hot water would likely have a better chance of performing any sort of cleaning action than water with ice in it.

If you truly want your holding tanks clean, the only real solution is to have them cleaned by a professional who uses a high-pressure, hydro jet system. With the special cleaning heads used, most tanks will end up as clean as they were when they were first installed at the manufacturer’s plant. And your professional will go over the processes and procedures you should be doing to keep your holding tanks clean and worry-free.

Jim Tome, Owner

Jim Tome, Owner

Hi, I'm Jim Tome and, along with my wife, Debbie, the owners of Kleen Tank LLC, the national leader in RV holding tank cleaning service. We've been RVers like you since 2004 and have traveled all over the U.S. in our Airstream travel trailer. We started the business about twelve years ago and have cleaned tens of thousands holding tanks in thousands of RVs. From tiny weekend travel trailers to monstrous fifth wheels to luxurious motorhomes, I've seen just about every situation there is with RV holding tanks and waste systems. I hope you enjoy our articles; I try to post at least one per week and we've got a great library of them to cover just about every problem. Enjoy!


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