Top 5 Myths About Your RV Tanks

If you spend enough time around RV owners, you’ll start to hear the same pieces of “advice” repeated over and over again. Some of it is harmless. Some of it is outdated. And some of it can quietly wreck your tanks without you realizing why things are starting to smell… or back up… or refuse to drain.

At the National RV Training Academy, we see these issues every single week. I’m Sue Rasmussen — an instructor here at the NRVTA and the owner of Royal Flush RV, where I make a living cleaning black and gray tanks that have been pushed way past their limit. After years of doing this job, I’ve learned just how deeply rooted some of these myths are.

Today, let’s clear the air — literally — and look at the five most common RV tank myths, along with the real truth behind them.

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Myth #1: “Just throw some ice in the tank and it will scrub everything clean.”

This one has been traveling through campgrounds for years. The idea sounds logical enough: dump a bag of ice into the tank, hit the road, and let the chunks scrape all the gunk off the inside walls.

Here’s the problem:
the ice melts almost instantly. Within a minute or two, there’s nothing left but cold water sloshing around — and cold water doesn’t magically scrub tanks any better than warm water.

If you want the same effect without wasting money on ice, do this instead:

• Add a few gallons of water to the tank
• Add your preferred tank treatment
• Let normal road movement do the rest

The only thing the “ice method” reliably cleans out is your wallet.

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Myth #2: “If it smells bad, just add more fragrance.”

This is probably the most common mistake I see.

When an RV owner starts noticing odors, the first reaction is usually to grab a stronger chemical — something blue, something green, or something with a tropical scent printed on the bottle — and pour in even more.

But all that does is mask the problem, not fix it.

Think of it this way:
We’re not trying to make the bad smell smell better.
We’re trying to remove the cause of the smell in the first place.

If a tank is producing odor, that means it needs to be rinsed, treated properly, or in some cases professionally cleaned. When everything is working the way it should, you shouldn’t smell your tanks at all — not inside your rig, and not standing over the toilet.

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Myth #3: “Leave the gray tank open so you don’t have to dump as often.”

Most people leave the gray valve open because it seems convenient. Showers, dishes, hand washing — all that water can drain freely without ever filling the tank. Simple, right?

Unfortunately, this is one of the quickest ways to create a nasty, sludgy mess.

When the gray tank stays open:

• Grease, soap scum, food particles, and oils stick to the sides
• Bacteria grows and thickens
• Black mold forms a slimy coating
• Critters (yes, actual critters) can crawl up from the sewer line and make a home in the tank

I’ve pulled out nests, pods, and bug clusters you truly don’t want to imagine.

So the rule is simple: Keep the gray tank closed until you’re ready to dump.

There are two exceptions:

1. Heavy shower use during a big family gathering — leave it open until everyone finishes, then close it.
2. When running a dishwasher or washing machine — these appliances can overwhelm a gray tank quickly, so keep the valve open while they run and close it afterward.

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Myth #4: “The tank monitor tells you everything you need to know.”

If you’ve owned an RV for more than ten minutes, you’ve probably heard someone say, “Those tank monitors never work.”

The truth is they do work — but sludge, grease, paper, and buildup stick to the sensors and make them unreliable.

A sensor reading “empty” might still mean your tank has layers of buildup inside. A reading of “full” may just mean something is clinging to a sensor.

Monitors are helpful, but they only offer part of the story. Regular rinsing, using treatment properly, and periodic professional cleaning are what keep the entire system working the way it’s supposed to.

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Myth #5: “Gray tanks are just soapy water — they don’t need attention.”

This one surprises people the most.

Many RV owners obsess over their black tank but completely ignore their gray tank.

But after years of cleaning them, I can tell you:
gray tanks are often far nastier than black tanks.

Why?
Because gray tanks collect:

• Food particles
• Cooking grease
• Soap scum
• Shampoo and body oils
• Hair
• Toothpaste
• Skin cells
• Detergents
• And everything else that rinses down your sinks and shower

I call it the petri dish — because that’s exactly what it becomes.

I’ve emptied gray tanks that looked like:

• Thick black mud
• Chunky potato soup
• Sludge you could scoop with a shovel
• Clumps of material too large to have ever fit down the drain

If that’s what your tank is holding, imagine the smell.

Treat your gray tank just like your black tank: rinse it, treat it, and maintain it regularly.

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The Bottom Line

RV tank care isn’t complicated, but it does require the right habits. When you ignore the myths and stick to what actually works, you’ll:

• Prevent odors
• Avoid clogs
• Keep sensors working longer
• Extend the life of your tanks
• And keep your whole rig healthier and more comfortable

Taking good care of your RV tanks doesn’t just make your camping trips better — it saves you money and frustration in the long run.

And that’s your Tech Tip Tuesday.

Top 5 Myths about your RV Tanks