Tuesday, October 4, 2022


New RVer asks: Should I use holding tank treatments?

By Russ and Tiña De Maris

“I stink, therefore I am,” says my philosopher. He lives under my RV, and travels everywhere with me. He is a rather nondescript fellow, about six feet tall, four feet wide, and a thin six inches thick. He seems to prefer a dark suit, in fact, every time I lay eyes on him, he’s laying about, clad in the black skin of plastic suited to folks of his kind. Although he is never invited inside, from time to time he does–in an awful way–make his presence known. He is a windy fellow, and many of my associates simply state, “He’s full of it.” And so he is, for my friend the dark philosopher is a black water holding tank.

As much as I try and force him to keep his ideas to himself, he does on occasion air his opinions. Usually my better half, she with the more sensitive of noses, is the first to complain. “You’ve got to do something about this!” she’ll yelp, making a rapid exodus from our little room of rest. It is perhaps the torture stake of the male species, this job of being resident problem solver.

DescartesTo keep my dark friend happy, I feed him a gruel of enzymes and bacteria, guaranteed to be “earth friendly,” and to relieve my friend of unwanted odors. To be sure, when it doesn’t work, I’m not sure who makes a bigger stink–my tank, or my wife.

Such is the sad proposition for all who RV. We must play the roles of many professions, and “sewage treatment plant operator,” is probably not our favorite. Let the “job” go, and trouble is sure to follow. Smelly holding tanks will not go away on their own. Hence, the huge line up of holding tank “treatments” for sale at any RV supply house or Walmart you can mention. What works? What doesn’t?

Want to stir up a controversy around a friendly RV campfire? Just put to RVers together and ask them what holding tank treatment to use. So here we go, adding more fuel to the fire. But the fuel we add is not only from our own years in the lifestyle, but from research by generally recognized sources.

cat fightThree areas of dealing with black water should concern RVers: Keeping odor at bay; ensuring solids don’t cause a ‘hang up’ in the tank; being good stewards of the earth with whatever we “output.” What choices we make in terms of treatment (or lack thereof) will affect all three of those areas.

Odor from black water comes from the naturally stinky nature of what we put down the pot. Some holding tank treatments deal with that by masking the odor with perfumes or other deoderants. Others deal with the smell by reasoning this way: Since the breakdown of the waste is what’s causing the smell, stop the breakdown and you’ll stop the smell. These “biocides” do just that: They kill all bacterial action in the holding tank, the wastes stop breaking down, and the odor, to some degree stops. How well these work in really killing the odor is rather subjective, and can certainly be affected by outdoor temperatures.

So what’s the drawback with a biocidal treatment? They may have a limited affect on the odor level, they allow a continuing buildup of solids in your holding tank that may, over time, cause a clog. And from the third concern, some biocidal treatments can harm sewage treatment plants (where your tank contents eventually wind up) and even the environment. To that end, “treatments” containing formaldehyde are almost universally banned by RV parks.

What treatments use biocides? A close read of the label (and sometimes by looking up a Materials Data Safety Sheet on the Internet) may show you. These are common biocides that have been used by the industry:

Bronopol: a bacterial pesticide.

Dowacil: another bacterial pesticide, one which the EPA says should not be discharged into to sewer systems “without previously notifying the local sewage treatment plant authority.”

Glutaraldehyde: Also known as embalming fluid. This material retards bacterial action.

Paraformaldehyde: A kin folk of formaldehyde and one that’s extremely toxic to humans.

Para-dichlorobenzene: The stuff you’ll smell in urinal cakes and moth balls. It’s a known carcinogen and drinking water contaminant.

Where does this leave the RVer who wants a smooth running holding tank that won’t run him out of his rolling home with a bad smell? Some RVers tell us they don’t use any sort of holding tank treatment at all. Almost universally among these we find that most thoroughly flush their black water holding tank every time they dump it, and few venture into hot climates.

Other RVers say they make their own treatments using everything from water softeners and soap to folks who pour huge quantities of bleach down the stool. We’re obviously in no position to evaluate these “moonshine” treatments. We can say that those who pour caustic chemicals like bleach down into their holding tanks are running a good gamble on how long they can treat their wastewater this way before they wipe out their holding tank seals, and possibly the metal rods that control the dump valves.

Others say they find that bacterial, enzyme, or a combination of both, in holding tank treatments work for them. In our experience, we’ve found bacterial-enzyme treatments to be quite effective in keeping the odor down, and in keeping the tank free of build up. For years we spent months on the desert, never moving the RV (hence not rinsing the tank for months at a time), and had few problems.

We did have one foul smelling experience when the combination of heat and non-motion did “shut down” the bacterial action in our tank. That was bad! To get out of that problem we had to empty the tank and fill it completely with water and a large dose of baking soda. After 24 hours we emptied the tank, then started using it again with a fresh dose of bacterial-enzyme treatment. The odor was gone, and we were happily back in business.

Bacterial and enzyme based tank treatments will not harm any sewage treatment system, be it a big municipal system or a campground septic tank system. However, if you have used biocide treatments before, you’ll need to thoroughly rinse the holding tank before adding the new treatment. The same is true if you use bleach in your tank–it will kill the “good guy” bacteria.

Regardless of the treatment choice you make, stick with good holding tank care: Keep your black water tank valve closed and dump only when the tank is at least 3/4 full. Use plenty of flush water. Don’t put undigested wastes down the toilet. We say that because we know of some who think it’s fine to empty out those “little dabs” of food leftovers into the toilet. Nyet! Rinsing your tanks between use is not a bad idea, but certainly not a necessity.

What about treating your gray water tank? Few RVers ever do much of anything about treating their gray tank. We recommend you abstain from pouring grease down the drain, but for the most part, a gray tank will give you few problems.



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