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Where Does Waste Water in an RV Go?

A woman refilling the RV water tank for their convinience with a full galloon.

It’s difficult to think about waste water in an RV without picturing the iconic scene from the movie RV. In the movie, Bob is attempting to drain the waste water tank.

Unfortunately for Bob, and hilariously for us, the connection comes loose. Waste water, which is essentially poop, explodes all over the Bob.

The “poop geyser” scene is obviously something you’ll want to avoid during your own RV adventures. Understanding your RVs waste water system is essential for avoiding this and other mishaps.

Types of RV Water Tanks

An RV has three different water tanks. These are fresh, gray, and black water tanks.

Fresh Water Tank

The fresh water tank is where the water for the RV is stored. Water that is used in the sinks, toilet, and shower all originates from this tank. Each time you fill up your water tank, this is where the water goes.

These tanks are typically made from polyethylene plastic. They can hold anywhere from 20-100 gallons depending on the size of your RV and model.

Grey Water Tank

Waste water from your sink and shower goes into the gray water tank. When you use water, it goes down the drain, and into the gray water tank.

Toilet water is excluded from this, as it goes into a separate tank. These tanks are typically about 50 gallons in size.

Black Water Tank

Now for the tank no one wants to think about. Your toilet water goes into the black water tank. Tanks can range from 40-70 gallons. Black water is placed in a separate tank because it must be dumped in areas designated for black water.

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Many campsites allow gray water to be dumped into grassy areas, but black water must be disposed of more carefully for obvious reasons.

Dumping Waste Water

A man dumping waste water from his small RV at the dumping station.

When dumping waste water, the first step is to find a place that allows you to dispose of it. You’ll need to find a campground that provides dump stations for gray and black water.

The Dumping Process

Before you begin dumping, you’ll need a sewer hose and a pair of gloves for sanitary reasons.

First, you’ll hook the hose to the black valve on the RV. Then, hook it to the valve at the dump station. Double check the connections before draining the tank, to avoid your own poop geyser scene.

Pull the tank valve, which allows the tank to drain. Once it’s completely drained, turn the valve off.

Next, you’ll disconnect the hose, and then repeat the process for the gray water tank.

You should always empty the black water tank first because the gray water cleans the hose of the black water residue.

Next, you’ll need to refill both tanks with clean water. Then repeat the dumping process. This helps keep the hose and tanks clean and sanitary. You can also dump RV sanitizing chemicals down the drains and toilet after dumping.

This helps prevent bacteria growth, and offputting smells that can come from your drains.

How Often Should Tanks Be Emptied?

A RV is emptying it's water waster into the drainage so it can be refilled again.

How often your waste water tanks should be emptied will depend on a few factors. This includes the size of your party, the size of the RV, and how much water you are using.

The Size of the Party Traveling

First, how many people are traveling in your RV. If you have a family of 5, you’ll use much more waste water than you would if you only had one traveling companion.

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Tank Size

The other factor is the size of your tanks. This is often relative to the size of the RV. Smaller travel trailers will have smaller tanks, and larger RVs will have larger tanks.

Use

How much you use your water systems is also a factor. If you are showering at a campground, you’ll use less water than if you are showering in your RV for example. The less water you use in your RV, the longer you can go without dumping the waste water.

How to Know When Your Tank is Full

An traveler adult man refilling the water tank of his RV.

Most RVs have a tank sensor that will let you know when the tank is getting full. Older RVs may not have a tank sensor.

If you are just beginning your RV journey, or your RV doesn’t have a sensor, you can wait for a clearer indication that the tanks are full. Just wait until the water begins to back up into your sink, shower, or toilet.

Of course, when this occurs, you’ll need to empty the tank as soon as possible. This can be a bit unpleasant when your black water tank fills.

You’ll notice a smell to say the least. However, you should be able to get a feel for when the tank is close to full fairly quickly.

Does the Tank Have to Be Full Before Emptying?

The tank doesn’t have to be completely full before you empty it. It’s best to avoid filling the tanks to the point of backup, just for the sake of convenience.

However, the tank should be at least 2/3 full before emptying. This is particularly important during the winter. Tanks are more likely to freeze during emptying if they don’t contain a lot of water.

A full tank also uses gravity to remove all of the contents from the tank. The last thing you want is the tank not emptying completely. The older matter will begin to smell, particularly the black water tank.

Close the Valves

You’ll need to close the valves after emptying the tanks, even if you are connected to sewer at your campsite. Leaving them open can cause a clog.

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In the winter, you  may end up with a poopcicle, which is unpleasant to say the least.

Tips for Managing Your Water Tanks

A man taking a bath outisde his RV using a shower while boiling some water.

The tanks do require occasional maintenance to keep everything in good working order.

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Fresh Water Tank

The fresh water tank is relatively user friendly. However, there are a few things to be aware of. You should insulate the fresh water hose in very cold weather to prevent freezing. In very hot weather, you may need to dump your fresh water tank to prevent stagnation.

If your fresh water tank begins to smell, you can clean it with bleach. Use 1/4 cup bleach for every 15 gallons of water the tank holds. Run the bleach water until the tank is emptied.

Allow it to sit for 24 hours. Refill your tank, and run water until the bleach smell is gone.

Grey Water Tank

Your grey water tank has a small drain. Be careful not to allow food particles into the system. Even small pieces of food can cause big problems.

Black Water Tank

Only use 1 ply toilet paper in your RV. It’s not luxurious, but it does help prevent clogs. Add water to the toilet bowl before flushing, and be sure to flush regularly. You should also sanitize your tank, preferably after each dump.

Lastly, you can clean the system by putting a garden hose down the toilet and running water. This helps keep the system clean and prevent buildups which can cause clogs.

Managing RV Waste Water

A man putting a water tank inside his RV for their necessaties while travelling.

Managing your RVs waste water isn’t that difficult or complicated. It does require regular emptying and occasional maintenance to keep things running smoothly, however.

Once you get the hang of caring for your waste water system, you won’t think twice about it.