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The Average RV Water Tank Size – Fresh, Gray, and Black

If you’re new to RVing, you quickly learn that RV water tanks come in all different sizes and colors. Knowing the role and size of your tanks is important and greatly impacts how you use your RV. Since each tank has a job, they work together to allow RVers to go camping and travel while minimizing any inconveniences.

Today, we’ll chat with you about RV water tanks and look at the role of each one and their size. And we’ll share a tip or two regarding tanks and your RVing adventures. Let’s get started.

What Are the Different Types of RV Water Tanks?

As we said, each of your RV water tanks has a job to do. No tank is more important than the others. They play an important role in creating a smooth RVing experience for you and your RV. Let’s look at the different types of RV water tanks and why you’ll likely be glad your RV has them.

Fresh Water Tank

The fresh water tank on an RV stores clean, potable water for using faucets, toilets, and showers. These tanks typically range from 10 gallons in smaller RVs to over 100 gallons in large rigs. 

If you spend most of your time in RV parks or campgrounds with a water source or connection at your site, you likely won’t use your fresh water tank all that often.

On the other hand, an RV fresh water tank is essential for various traveling scenarios. Having fresh water can be helpful if you want to pull over to use the restroom in your RV instead of gambling with a sketchy or unclean truck stop bathroom. 

You’ll also have plenty of camping experiences (dry camping, boondocking, etc.) where you’ll need to be self-sufficient for water.

Gray Water Tank

An RV gray water tank is a storage tank mounted to an RV’s frame. These tanks store any water that goes down sinks or shower drains in an RV. As a result, these tanks typically contain a generous amount of soapy water from washing hands, washing dishes, and showering.

Many RVers underestimate the potential odors this tank can create when not maintained properly. Letting water that contains food particles and oils from your skin sit too long can cause these tanks to reek horribly.

Imagine finishing dishes and leaving the dishwater in your kitchen sink for several days. You wouldn’t expect anything less than a serious stench.

FYI: Can you dump grey water anywhere?

Black Water Tank 

The black water tank is another storage container mounted to the frame of an RV. Its job is to store the solids and liquids flushed down a toilet. This means these tanks typically contain a mixture of sewage, toilet paper, and water. 

Because of its contents, this is the RV tank feared by many new RVers.

While it can initially be intimidating, it becomes easier the more you dump your RV’s black water tank. You should always take your time, check your connections, and empty them in a suitable location. 

Because they can quickly develop an odor, you’ll want to ensure you keep these clean and regularly maintain them.

What Is the Average Size of RV Water Tanks?

The size of RV water tanks greatly depends on the type and size of an RV. A smaller travel trailer or Class B motorhome may only have a 15 or 20-gallon fresh water tank. In addition, some tiny rigs only have five-gallon gray water tanks and use alternative toilet options to avoid needing a black tank.

On the other hand, you’ll find some larger travel trailers, fifth wheels, and motorhomes with huge RV water tanks. A mid-sized RV typically has tanks ranging from 30 to 50 gallons, and the largest RVs will have 60 to 100+ gallon tanks.

Even if you don’t plan to use them regularly, you want to consider the size of your tanks when shopping for a rig. Some campgrounds, particularly in the northern states that experience extreme winters, do not have water connections at every campsite.  

You’ll need to fill up at a potable water station on the way to your campground. The more water you can store, the less you’ll need to worry about managing your water or running out in the middle of your trip.

What Size Fresh Water Tank Do I Need for an RV?

You need to consider a couple of things regarding the fresh water tank size you’ll need. First, you must know how and where you plan to use your RV. If you have no interest in boondocking, dry camping, or self-sufficiency, you don’t need a huge fresh water tank. 

If you RV in campgrounds where you always have a water connection nearby, you don’t need to worry about storing water. On the other hand, if you want to give boondocking or dry camping a try, you’ll appreciate larger water tanks in an RV.

Another thing you should consider is how many people will travel with you. The more people in your RV, the more water you’ll use. 

It makes sense that a family of five will use more water than a solo traveler. If you’re RVing with kids, you need to remember that they’re like magnets for dirt when out in the great outdoors. They may need to get sprayed down or have nightly showers, which can use a generous amount of water.

Can You Fill Fresh Water Tank With Tap Water?

In most cases, the water that comes from a tap is no different than that from a home’s outside water spigot. As long as the tap water is clean, filling an RV fresh water tank with tap water is perfectly acceptable.

We’ve seen RVers fill their fresh water tank by dumping jugs of tap water into them. While it can take a lot of time and require more effort if you can’t connect your RV to the water source, you’ll do what you must.

How Long Can You Leave Black Water in Your RV Tank?

How you use your RV will determine how long you can leave black water in an RV tank. A good rule of thumb is to dump your tanks at the end of every camping trip, especially if you’ll have more than a week between uses. 

You may come back and discover a horrible smell in your rig or get a whiff of a putrid smell when flushing the toilet.

How Long Do Water Tanks Last on RVs?

RV water tanks typically last 10 to 15 years under normal circumstances. We have heard RVers experiencing issues with tanks developing cracks, leaks, and other issues. However, while these situations do occur, they aren’t very common. 

Most water tanks in an RV can last for a decade or more and never experience any issues. If you sanitize and maintain your fresh water tank, it’ll last much longer.

Can You Drive With a Full Water Tank?

Driving with full water tanks is a hot topic in the RV community. On one side of the debate are the individuals who have done it for years and never had an issue. On the other side are those who never have and will never travel with full tanks. 

Unfortunately, the best answer we can give is to check with your manufacturer.

In our experience, we’ve found RVers and manufacturers on both sides. Some manufacturers have built rigs to handle traveling with full tanks; others have not. 

As a result, you could risk damaging your rig or voiding a warranty if you drive with full water. Full tanks also weigh more which you might need to consider.

 A quick phone call to your RV manufacturer’s customer service department will answer any questions.

But your RV water tanks don’t need to make you feel intimidated. You’ll get the hang of them quickly.

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