I know I’m supposed to be working on the tank additive experiments now (and I am, I promise), but when I had the idea for this detour, I couldn’t resist.
I’m sure we’ve all heard that advice at one time or another to dump a bag of ice into the RV black tank to “scrub it out” or “knock things loose”. On the surface, it makes sense. But does it really work? I had to find out.
Since I had the black tank simulator, and my old pickup truck, I put this advice to the test. By the way, I love that truck – I’ve had it since 1987! Anyway, I constructed a rig to hold the tank still in the truck while I drove around, and I put two cameras on it. I even got a camera INSIDE the tank to catch the action. I went with a purple simulated waste this time, using one of the new recipes based on a paper by NASA scientists. (Yes, they have scientists that develop simulated waste.) After that, it was buy some ice and drive around for an hour or so.
But did it work?
Short answer: Maybe kind of, but not really all that great.
I wanted to go all “Myth-Busters” on it and declare the old advice a hoax, but in the end, you can get a very limited scrubbing action with the ice cubes. But that comes with a few caveats.
1: You have to drive your RV like a demon
I drove my truck like a madman. Even with that, I was unsuccessful in getting the ice very far up the sides of the tank, or in completely knocking all the waste off. You WOULD NOT drive your RV like I was driving. Trust me. And even so, in the video, you’re just seeing the highlights. Most of the time, the ice just sat there.
2: You have to use the right amount of ice
If you put too much ice in the tank, it will kind of pack itself in, and not move at all. You want enough to cover the bottom, and then a little bit more than that. But the trouble is, most of us can’t see into the black tank to know how much that is.
3: You have to use the right amount of water
You want the ice moving, but not floating. If the ice is floating, well, it’s floating, and anything underneath the ice is just soaking. If soaking is what you’re going to do, then even room temperature water is more effective than ice water.
4: Even if you do everything right, it’s pretty darn weak
Scrubbing works on abrasion, but ice and water is a very low-friction environment. The ice just doesn’t smack into things very hard. Most of the time, the stuck on waste was pushing the ice, and not the other way around. Now, you might be able to improve on that by freezing up a solid block of ice that you can get down the toilet. But by the time you’re making special three pound ice cubes that you can fit down your RV toilet… well I’m just going to say you’re going too far.
By now, I’ve seen enough of these experiments to know that most of the cleaning action you saw was just due to the water, and not the ice. In fact, if you really had some stuff baked on in there, you’d be better off going the other way, and pouring HOT water down the tank. Think about it: you’ve never seen anyone try to clean a casserole dish by putting ice cubes in it, because everyone knows it won’t work. This is no different.
So what’s my take?
If you need to clean stuck on material out your black tank, and you don’t have an in-tank rinsing system – save your money, save your ice, and save your gas. Just soak it. It will work just as well.
Enjoy the video. This one is only 8 minutes long!! (And Stef’s in it, so it’s prettier than my usual videos.)