RV owners have argued about black tank treatments for years. Some use them after every dump, while others say plenty of water is all you need.
A side-by-side comparison gives us a better look at that debate. One treatment clearly broke down more solid material and helped more of it leave the tank. But the test also showed something else: rinsing made a major difference, and I’d argue the test was missing a major component.
So the real question is not just whether black tank treatments work. It is whether they help enough to be worth using at all.
Let’s find out!
What Black Tank Treatments Are Supposed to Do
Not every black tank product works the same way.
Some treatments use enzymes, bacteria, or a combination of the two to break down waste and toilet paper. Others focus more heavily on odor control. There are also surfactant-based methods that aim to make tank contents easier to move without breaking down the solids.
For example, Thetford says its enzyme-based Aqua MAX treatment breaks down and liquefies waste and toilet paper while controlling odors. Dometic’s MAX Control Natural uses an enzyme-and-bacteria formula that the company says breaks down waste and controls odors.
Those are manufacturer claims, however. They tell us what the products are designed to do, not how much difference an average RVer will see compared with using water alone.
That question is harder to answer.
The National RV Training Academy Says Bacteria and Enzymes Can Help
The National RV Training Academy recently addressed the debate in one of its Tech Tip Tuesday videos.
The instructor’s basic position was that there is nothing wrong with using bacteria or enzymes in an RV black tank. Waste already introduces bacteria into the tank, and additional treatments can help break down solids that might otherwise be harder to remove.
He also stressed something both sides of the debate generally agree on: water is a major part of proper black tank management.
That advice lines up with guidance from RV manufacturers. Keystone recommends adding water before flushing and keeping the black tank valve closed between dumps so solids do not collect on the bottom while liquids drain away.
One part of the NRVTA explanation needs a little clarification, though.
The instructor points out that bacteria are already introduced into an RV black tank through human waste, so some biological breakdown can occur even without adding a treatment. He compares that activity to what happens in a septic tank, while noting that an RV tank holds the waste for a much shorter period.
Technically, an RV black tank is a holding tank rather than a septic tank. But his larger point is reasonable: bacteria are already present, and biological activity does not suddenly begin only when an RVer pours a treatment into the toilet.
That still leaves a separate question, though. If bacteria are already present naturally, does adding more bacteria or enzymes make enough of a difference to justify using a treatment?
RV Tips & Travels Built Two Tanks to Test the Idea
A more hands-on look at the issue came from RV Tips & Travels, which built two simulated 32-gallon black tanks.
Both containers were polyethylene, the material commonly used for RV holding tanks. They were vented and positioned on an angle toward their drains.
He then added equal amounts of water, septic-safe toilet paper, dog food, and peeled bananas to both tanks over several days. The bananas and dog food were used as substitutes for larger and smaller solid waste.
One tank received Liquified RV Toilet Treatment.
The second received a homemade Pine-Sol and Calgon mixture recommended as a surfactant treatment. The idea behind that method is not to break solid waste apart, but to reduce surface tension and help material move through the tank more easily.
The two tanks were otherwise treated alike during the test.
The Waste-Breaking Treatment Clearly Changed the Contents
Before dumping the tanks, there was an obvious difference.
Most of the solid material in the Liquified tank had broken apart. Some recently added banana material remained, but much of what had gone into the tank was no longer recognizable.
The surfactant tank looked very different. The dog food had absorbed water, but the larger solid material remained largely intact.
Both tanks had received the same amount of test material and water.
Under these test conditions, there is little question that the waste-breaking treatment did something.
That finding is also consistent with how Liquified describes its product. The manufacturer calls it an enzyme-based treatment designed to break down solid waste and toilet paper.
The more interesting question was what happened when the tanks were emptied.
Breaking Down the Solids Helped During the First Dump
Neither tank emptied completely when the drain valves were opened.
As the water level dropped, solid material farther from the drain stopped moving toward the outlet. A substantial amount of intact material remained in the surfactant tank.
The Liquified tank also retained some material, but noticeably less was left behind because much of the original solid material had already broken apart.
The demonstration helps explain something that can be easy to overlook when dumping an RV tank.
Pulling the black valve does not create a giant vacuum that pulls everything inside toward the sewer hose. Waste has to be carried toward the outlet by moving liquid. As the tank empties and that movement decreases, material that has not reached the drain can remain behind.
Smaller material suspended in the liquid has an advantage over a large piece of solid waste sitting several feet from the drain.
So, based on this test, breaking waste into smaller material appears to improve how much leaves during the initial dump.
But the next part of the experiment was even more telling.
One Rinse Made a Huge Difference
After the initial dump, both tanks still had material inside.
The tester then partially backfilled each tank with clean water and dumped them again. He did not refill the tanks completely. The water level was brought to roughly 20 to 25% of capacity before the valves were reopened.
A large amount of the remaining material came out after that single rinse.
The surfactant tank still contained some recognizable solids afterward. The Liquified tank reportedly had no visible solids or paste remaining.
That result supports the case for a waste-breaking treatment, but it also shows just how much difference adding more water and dumping again can make.
The creator reached a similar conclusion. He preferred the waste-breaking treatment after the test, but also recommended rinsing the tank at least once after dumping.
For many RV owners, the rinse may be the more useful lesson from the entire experiment.
There Was One Big Option Missing From the Test
The experiment compared two approaches:
- A treatment designed to break down solid waste
- A surfactant mixture designed to help intact solids move
It did not include a third tank containing nothing but waste and water.
That leaves the biggest practical question unanswered.
Suppose a third tank had received the same amount of toilet paper, bananas, dog food, and water, but no treatment. What would have remained after the first dump? More importantly, what would that tank have looked like after the same 20 to 25% rinse?
We do not know.
That is a significant limitation because the tanks in the test were already approximately 90% water before they were dumped.
Liquified clearly outperformed the Pine-Sol and Calgon method used in the test. The experiment does not establish how much better it would perform than water alone under the same conditions.
The Test Was Useful, but It Wasn’t a Real RV Black Tank
There were a few other differences worth keeping in mind.
The drain opening on the test tanks was roughly six inches above the bottom because the shape of the storage containers prevented it from being placed lower. The tester argued that this did not significantly change the outcome because solids had stopped moving before the water reached that level.
Still, RV holding tank shapes and drain locations vary, and a six-inch difference in outlet position is not insignificant in a test specifically looking at what remains on the bottom.
The simulated tanks also stayed in one place.
A real RV may travel miles before reaching a dump station. Braking, accelerating, turning, hills, road vibration, and bumps can move water and waste around inside the tank.
Then there are the test materials themselves. Bananas and dog food provide an easy way to see what is happening, but they are not human waste. The experiment is a useful demonstration rather than a controlled scientific study.
None of those limitations make the results meaningless. They simply narrow what can reasonably be concluded from them.
Independent Evidence for RV Tank Treatments Is Limited
The RV industry sells plenty of bacteria and enzyme products, but independent research showing that RV owners need them is surprisingly thin.
The University of Minnesota Onsite Sewage Treatment Program discussed research involving RV wastewater and several holding tank products. When asked specifically about the claimed benefit of enzyme-based treatments, Dr. Sara Heger said there were no third-party proofs showing that holding tank enzymes really break down waste.
Her preference was no holding tank treatment at all.
That statement may seem to conflict with the RV Tips & Travels experiment, but the two sources are answering slightly different questions.
The YouTube test showed that one commercial treatment visibly broke down bananas, dog food, and toilet paper better than the surfactant mixture tested alongside it.
The University of Minnesota discussion points out the lack of independent evidence establishing how much benefit those products provide in actual RV use.
Both can be true.
A product can have a measurable effect without being necessary for proper tank operation.
So, Should You Use a Black Tank Treatment?
There is a reasonable case for using one.
A product that breaks larger waste into smaller material may make it easier for some of that material to leave during the first dump. The RV Tips & Travels experiment provides a useful demonstration of that effect.
Odor control can also be a reason to use a treatment if your RV has an odor problem that is not being caused by a bad toilet seal, venting issue, or another mechanical problem.
But there is another question: Is the improvement worth paying for?
That depends on how much benefit the treatment provides in your RV.
At the time of writing, Liquified lists its 32-ounce bottle for $24.99 and calls for one ounce per 40 gallons of tank capacity after each dump. That works out to roughly 78 cents per standard treatment. The company recommends doubling the dose when temperatures are above 85°F. Larger refill bottles can lower the cost per treatment.
Seventy-eight cents does not sound like much on its own. For someone who dumps frequently throughout a long camping season, though, it becomes another recurring expense.
If treatment prevents clogs, improves odors, or noticeably reduces the amount of rinsing needed in your RV, that cost may be easy to justify.
On the other hand, if using enough water and performing one quick tank rinse already leaves everything flowing properly, paying for treatment after every dump may provide very little practical benefit.
That is the part the side-by-side experiment could not tell us because it never tested plain water.
“Does the product work?” and “Is the product worth buying?” are not quite the same question.
Water May Still Be the Most Useful Black Tank Treatment
The evidence points to a less complicated approach than many black tank debates suggest.
Use plenty of water when flushing. Keep the black valve closed between dumps. Allow enough liquid to build up before opening the valve. Dump the tank, then rinse or backfill it when your RV’s system allows you to do so.
A bacteria or enzyme treatment can be added to that routine. The RV Tips & Travels test gives us a reasonable indication that breaking waste down can make evacuation easier.
For RV owners who already use plenty of water and rinse regularly, a tank treatment may be more of an optional extra than a necessity. It may help break waste down faster, but the available evidence does not show that every black tank needs one to work properly. The more useful question may be whether the added benefit is noticeable enough in your RV to justify the ongoing cost.
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