Why Does My RV Have Two Black Tanks? 

The RV industry is one of the fastest-growing industries in the country. With great growth comes great innovation and new design ideas. One of these many design ideas and innovations is the addition of a second black tank on select RVs and models. While the addition of a second black tank is pretty common nowadays, many people still wonder what the purpose of two black tanks is. 

If your RV does have two black tanks, it’s because you have two bathrooms and two toilets on separate ends of the trailer. Each toilet in your RV needs its own black tank because it’s easier and more cost-effective to add a tank than running extra plumbing and sewage pipes on longer RV’s. 

Rather than questioning why your RV has two black tanks, you should instead be thankful. Having multiple black tanks means you’ll spend less time at dumping stations and more time enjoying your camper. Multiple black tanks also allow you to spend more time camping off the grid because your tanks won’t fill up as fast. 

Why are There Two Black Tanks on My Camper? 

The reason that RVs have two black tanks is to accommodate multiple bathrooms. In some cases where you have a massive camper, you might have up to three bathrooms, which means you’ll have three black tanks. As a general rule, you’ll have one black tank for every toilet in your RV. In most cases, it’s one or two, but don’t rule out the possibility of three down the road. 

Will I Always Have Two Black Tanks With Two Bathrooms? 

The proximity of your toilets will determine whether you have one or two black tanks. In situations where your bathrooms are very close, you might only have one black tank. However, RVs don’t have very much space in their frame area, which is where your tanks and plumbing pipes are located. As a result, there sometimes isn’t enough slope for sewage pipes if they run from one end of the camper to the other. When this happens, you’ll need two black tanks. 

Are Your Black Tanks Connected? 

If you have more than one black tank on your RV, they won’t be connected to each other. Water and waste that goes into your black tank will be unclean, disgusting, and potentially toxic, which means it has to stay separate from everything else. 

How to Drain Multiple Black Tanks 

If you have multiple black tanks, it means that you’ll have to drain them individually. While this might seem like a time-consuming task, draining multiple black tanks is actually quite simple. 

1. Purchase individual sewer hoses for each tank, and connect one end of them to the tank.
2. Purchase a Y coupler fitting that’s specific to RV hoses and connect it to each of your sewer hoses. 
3. Purchase a third sewer hose to go from the Y to the sewer drain at your campground. 
4. Connect one end of the third sewer hose to the bottom of the Y fitting and the other end to the campground sewer pipe. 
5. Drain each black tank individually, and never have both ports open simultaneously to prevent backflow. 

Here are two products that will solve your problem about connecting both of your tanks to one sewer connection:

• Wye adapter with 20′ of hose
• Wye Adapter without Hose

Does My RV Have Other Holding Tanks? 

In addition to your black tanks, your RV will feature several other holding tanks for waste and water. 

Freshwater Tank 

As its name indicates, your freshwater tank is meant to hold fresh city water for later use. You can use this water while you’re off-grid for showering, drinking, or washing dishes. 

Grey Water Tank #1

The other type of wastewater holding tank that you have is a grey water tank. Grey water tanks catch and store wastewater from every plumbing appliance aside from your toilet. This includes water from your kitchen sink, shower, washing machine, and bathroom lavatory. 

Grey Water Tank #2 

Depending on the size of your RV, you might have two grey tanks in addition to your two black tanks. In fact, if you have two black tanks, you’ll almost certainly have two grey tanks because you’ll need one for each bathroom. 

Even if you only have one bathroom, you’ll have two grey tanks if your RV includes a washer and dryer hookup. Because most washing machine hookups are towards the end of a camper and not in the middle, it requires its own grey water tank. 

It’s important that you drain each of your tanks in sequence rather than attempting to drain multiple tanks at once. Backflow from one tank into another can lead to contamination, and you’ll have to pay big bucks for a professional tank cleaning. 

Wondering why you have 2 grey water tanks? Here we explain the 5 reasons.

Frequently Asked Questions 

Does RV shower water go to the grey tank or the black tank? 

RV shower water is considered grey water and therefore goes into your grey tank. Only toilet water and waste goes into your black tank. 

Does the grey tank drain into the black tank? 

The whole purpose of having separate black and grey tanks is to prevent them from draining into one another. Your grey tank drains directly out of the sewage port and doesn’t enter the black tank, because then black water could enter the grey tank. 

Why does my camper have 2 black tanks? 

Your camper will have two black tanks if you have two toilets because each toilet requires its own tank.