What’s A Typical RV Holding Tank Size?

Who doesn’t like going on road trips to beautiful locations? If you’re looking forward to going on a long drive, especially with family, RVs are your best friends. The #vanlife fever is not for nothing!

RVs are miniature houses on wheels that have all the conveniences of a stationary building. But as enjoyable as they are to live in, they come with their own set of problems. Being constantly on the road means you will need a consistent supply of plenty of food and water. Now, water needs to be stored somewhere so that you can use it later at your convenience.

RV holding tanks are the storage containers that hold your water. They preserve all types of water including the water that you drink as well as the water that you flush down the toilet. Maintaining these RV tanks thus becomes a necessary and inevitable part of owning an RV. Read on to understand the functioning of your RV holding tank.

Class A Customs 14 Gallon RV Waste Black Water Holding Tank WT-1400

Types of RV Holding Tanks

RVs usually come with three tanks that are located on the underside of the RV. This keeps everything running smoothly.

Fresh Water Tank

As the name clearly states, this tank carries clean, potable water that then comes out of the RVs sink faucets and showers. As long as you maintain your RV well, the water will be drinkable. Although its size depends on the type of RV you’re driving, this is the largest tank in comparison to the other two.

Black Water

This tank holds the wastewater that you flush down the toilet. It contains all the disgusting sewage and human waste.

Gray Water Tank

This is the wastewater that flows down from the sinks and showers. However, this water is relatively cleaner than black water as it contains soap residues or food particles. Thus, avoiding anything really nasty.

How To Know the Capacity of Your RV’s Tanks

Usually, you can just open the storage area of your tank to check its capacity, but that’s not always the case. If you’re unable to tell the capacity by simply looking at your tank, you can check the manual.

If you cannot access the manual, a simple internet search of the make, model, and year of your RV can help you find the required information. The tank sizes would be available on the manufacturer’s or seller’s website. RV manufacturers sometimes end up listing the capacity of each type of tank individually. Sometimes, they just note the water tank size such as 75-60-50.

This display format is typically in reference to your freshwater tank size, followed by the size of your gray water tank and then your black water tank, respectively.

However, contrary to popular belief, freshwater, black water, or gray water tanks do not come in any specific sizes. Their sizes vary depending on their manufacturers as well as the size of the RV they’re being used in.

Average Size of Freshwater Tanks

An average tank holds approximately 20–100 gallons (75 to 380 liters) of freshwater. A class A trailer, having the largest tank, will carry the most water, averaging at 72–100 gallons (280 to 380 liters).

Next in line, Class C trailers will carry 35–60 gallons (132 to 227 liters), followed by Class B trailers carrying 20–40 gallons (75 to 151 liters), and then fifth-wheel RVs carrying 60–80 gallons (227 to 301 liters).

The tinier RVs carry up to 40–60 gallons (150 to 220 liters).

Average Size of Gray Water Tanks

The dimensions and sleeping space of your RV often affect the measurements of your gray water tank.

Usually, across all RV models and trailers, gray water tanks have the capacity for carrying about 50 gallons (190 liters) of water, with Class A and fifth-wheel RVs being placed at the top of the table while Class B is placed at the bottom.

In a Class A RV, such a tank usually holds 39–60 gallons (150 and 230 liters) of water. In fifth-wheel trailers, the range is almost the same. Although there are some RVs that carry nearly 92 gallons (352 liters) in the gray water tank.

Class B motorhomes, although the smallest RVs on the list, usually hold between 8 and 34 gallons (30 and 130 liters) in the gray water tank.

Class C motorhomes may hold between 30 and 90 gallons (120 and 340 liters), among all other different measurements and sleeping arrangements.

The travel trailers also have a huge range of dimensions. The gray tanks in smaller RVs may be capable of holding 27 gallons (105 liters). The larger RVs might hold as much as 80 gallons (300 liters).

Average Size of Black Water Tanks

In most RVs, the black tank is usually more portable than the fresh and gray water tanks. However, it can fill up quickly depending on how much water you expel, how often you use the toilet, and for what purposes.

The dimensions and range of your storage tank also depend on your RV or camper. Usually, the black tank holds up to 18–63 gallons (70 and 240 liters) worth of water.

This tank in Class A trailers usually has a capacity of 30 – 50 gallons (120 to 200 liters).

If your Class B trailer has a black tank, it’ll probably be between 10 and 25 gallons (40 and 100 liters).

Class C motorhomes, which come in a wide range of fits, have black tanks that are between the measurements of 25–60 gallons (100 to 240 liters).

The fifth-wheel trailers usually have the largest black tanks that can hold up to 40–90 gallons (150 to 340 liters) when full.

You might come across larger tanks in bigger travel trailers; however, the black tank in these campers generally holds between 35 and 90 gallons (140 and 335 liters).

How to Maintain Tanks

Once you get the hang of emptying the tanks in your trailer, the process can go swiftly and smoothly. But merely emptying the tanks is not enough to ensure your tanks’ proper functioning. You also need to maintain them to avoid any problems in the future. If you keep maintaining your tanks consistently, they will last longer and work more efficiently.

In general, you need to regularly flush your toilet along with cleaning and sanitizing your tanks. This helps in keeping the system running smoothly and efficiently and completely free of problems.

Use household bleach to clean the tank

  • Pour 0.25 cups of bleach for every 56 liters of water in your tank.
  • You need to run the water until you start smelling bleach.
  • Continue to run until all the bleached water is out.
  • Leave your tank alone for about a day or so.
  • Refill your tank and run the water until the smell of the bleach is gone.
  • Use as normal.

How to Empty Black and Gray Tanks

Black Water Tank

To empty your black tank, you will typically need to go to an appointed dump station. You will find these in practically all business camping areas and generally in national as well as state parks. And if your campsite includes full hook-ups, you will also find a sewer hose attachment site there.

Make sure you do not dump your waste in places it isn’t supposed to be dumped.

Gray Water Tank

It is relatively easier to maintain your RV’s gray water tank than the black one, far less intimidating even. However, this does not mean that your gray water tank does not require effort while cleaning.

An RV gray tank is greasy as it takes in a lot of gross, sticky substances. This accumulation of grease, soap lather, food remains, etc. can result in odors that give a tough competition to the ones coming from the black tank.

The gray tank contains the remains of all disgusting things ranging from leftover food items, lather, or shampoo bubbles. All this might affect your holding tank sensors after a while and cause your tank monitors to give off false readings.

In certain extreme cases, these remains can even cause clogging. It is thus necessary that you clean your tank regularly and use an environment-friendly treatment while doing so.

Cleaning the gray tank is not very difficult. Automatic dishwashing detergents are easily available and are developed to easily break down all of the filth that has accumulated in the tank. This gel-type is easy to expel down the toilet drain and disintegrates and dislodges the greasy dirt.

Step 1: Put Detergent in Your Tank

In order to begin with cleaning your tank, make sure it’s a day when you are free enough to go on a long drive to a hook-up RV park. You need to start with a gray tank that is nearly semi-full, and pour a cupful of automatic dishwashing detergent gel into any of the sinks. (Make sure to not use standard dishwashing soaps such as Dawn or Palmolive. These will fill your tank with lather and you don’t want that happening.) Follow it up with some hot water, and make sure it is not boiling.

Step 2: Let the Detergent Sit For a Few Hours

Once the detergent is in your tank, start driving around. You can take this opportunity to spend a few hours having fun with your friends or family on the road. This will create splattering action in the tank, and the unpleasant gunk that has accumulated will then be broken down. The more hours you spend on bumpy roads the better, but just a few hours driving around should also be enough to get the job done.

Step 3: Dump the Dirt

On arriving at the hook-up camping site (or a dump station), you can pull the gray valve off and dump all the content of the tank.

There are chances that your tank might not get cleaned on the first try. In that case, you don’t worry. Feel free to repeat the above-mentioned steps the next time you go on a road trip, whenever you take one. Because of the minimal amount of money spent on this procedure, you don’t need to stress yourself by giving your tank a second sweep.

Once your tank is completely scrubbed, it should work totally fine. Any odors that you might have been previously experiencing should have been removed or at least reduced by now as well.


Living in an RV can be a lot of fun, although it can even get a little hectic sometimes, what with all the cooking and the cleaning involved. But, like with most things, consistency is key.

If you regularly clean your water tanks, you wouldn’t have to worry about bad water. The idea is to make sure that your tanks are thoroughly maintained to keep your road trips seamless and stress-free.

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