As RVers, we expect our black tanks to stink. But why do our gray tanks smell sometimes too? There are plenty of reasons and the solution is often easier than you think!

Let’s face it. RVing sometimes stinks! Unlike your home, waste tends to “stick around” until you get rid of it. And hot weather, unclean tanks, faults in your RV’s plumbing, and poor habits can only make things worse. So why are our tanks smelling and what can be done about it?

It’s a holding system, not a septic system

One of the first lessons we teach in our rally seminars and when speaking with customers during a cleaning service is to educate them that their tanks are intended to hold waste for disposal later, not hold it so that it can be broken down, like a septic system.

Think about it. What would drain more completely, faster, and without problems? A tank full of mostly water with “stuff” (waste) floating around in it or a tank of pancake batter?

Pancake batter?

Yep, that’s what that enzyme, harsh chemical, or biological is breaking waste down into, especially in black tanks. It happens in gray tanks too, but to a lesser degree. Gray tanks have their own problems, as we’ll see later.

So stop using those tank additives the RV store, dealer, or articles online are saying to use. Thousands of tank cleanings over seven years have taught us that you’re causing more problems than you’re solving.

Gray tanks have problems too

While we think of gray tank contents as mainly water and soap, there’s other things in their too. Human hair and skin, food waste and coffee grounds, grease and oil, toothpaste and soap, sand and dirt. Those gray tanks are as clean as you think and we’ve encountered many so stinky we had to “get some air” while we were cleaning them.

One of the worst odor causers in your gray tank, however, isn’t something you’ve flushed down the drain. It’s mold.

Hot, wet and dark

All holding tanks — black, gray and fresh water — tend to have three common properties: They get warm, they are wet or moist, and they’re dark. Add in airborne yeast, mold and bacteria and you have a virtual Petri dish of growth.

While emptying your tanks periodically will flush out most of what’s growing in their, some remains and starts to build up. And as the situation gets worse, so does the smell. This is especially true for RVers that leave their gray tank pulls open: the water or liquid seeps out and solids, waste and growing stuff is left behind, smelling up your RV.

So what’s the solution?

There are plenty of things you can do to reduce odors in your RV.

1. Get regular, periodic tank cleanings. We had to lead with this one, right? It’s a fact that annual and even semi-annual (for full-timers) professional tank cleanings will get — and keep — your RV’s holding tanks clean.
2. Use plenty of water. No matter what tank we’re talking about, using plenty of water will help to keep it clean. That means dumping your tanks when they are 90%-100% full (add water at dump time to max out volume). And “prime” your tanks with a few gallons of fresh water after emptying them. Even traveling with a few gallons of clean water in each tank will help to keep them clean and odors down.
3. If you use a tank solution, use a smart one. Avoid those enzymes, harsh chemicals, and biological concoctions that are designed to break down waste into sticky, smelly pancake batter. A great alternative solution is our recommended mixture of Calgon, Pine Sol, and water. Get the recipe and usage instructions here.

What about vents, traps, seals, and pipes?

The plumbing in today’s RVs is as diverse as RV types themselves. Some have traps and seals of varying efficiency and effectiveness. Almost all RVs have vent pipes (which tend to be good nesting places for birds, spiders and insects, clogging them up and reducing their purpose).

It’s a good idea to periodically check the plumbing of your RV, paying special attention to soft seals, traps, and vents. Some RVers even add special wind-activated attachments to their plumbing events that create a suction to reduce in-RV odors.

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