RV 101: RV Black Water Tank Guide

Your RV black water tank might make you want to hold your nose. Of the RV water tanks, the black tank is easily the grossest. That’s because all the wastewater from your toilet ends up here. 

With that in mind (but not for too long), that’s exactly why it is an essential part of the RV experience. So, how well do you know your blank tank? 

Let’s make sure you understand how it works and how to use it properly. If you ever need help with plumbing, though, be sure to call in an expert RV technician

Size and Scale

RV black water tanks come in an array of sizes. For instance, some class B motorhomes and trailers have smaller 18-gallon tanks. On the other hand, some larger recreational vehicles boast a 64-gallon black tanks. That makes sense, though, right? 

Just like your freshwater tank, smaller rigs have smaller tanks, and you find larger tanks on bigger rigs. However, that’s not the best way to estimate the tank size on a particular RV. If you need to find information on your RV black water tank, check the specs. 

Once the black tank is full, you basically have to find a spot to dump your tanks. Knowing the size helps you judge how long you can go between dump stations. This is especially important for boondocking, which often lands people at random stops. 

How to Use Your Black Tank

Luckily, you don’t have to think about your black tank all that much. Whenever you flush the toilet in your RV, it’s automatic. Still, there are a few things to keep in mind. 

  • Use a good amount of water: When you flush the toilet, be sure to use enough water. This helps to break down solids in the black tank, which avoids clogs. Moreover, it helps to reduce the smell.
  • Don’t leave your RV black tank open: When you have a destination with full hookups, you might be tempted to leave the tank open so that waste flows directly to the sewer. This is an awful idea because it allows all the liquid to drain away, leaving solids to dry and build a disgusting pyramid in the tank. It’s gross, frustrating, and a major problem in one nasty pile. 
  • Use RV toilet paper: Speaking of solids, be sure you buy toilet paper specifically for RVs. At the very least, use 1-ply toilet paper. Thicker TP doesn’t break down easily, which causes the tank to clog. 

How to Dump an RV Black Water Tank

You hit the road in your motorhome on your family vacation. A few days later, your black tank is full. What do you do then? 

Dumping the black tank is never a fun job. However, it’s not as bad as you might think. 

Connect the Hose

First, it’s a good idea to put on rubber gloves. This just helps to protect your hands. Then, locate the dump valves. 

  • Remove the cap from the dump pipe. 
  • Attach a sewer hose to the pipe. 
  • Secure the other end of the hose to the sewer drain (in the ground). 
  • If there’s no way to twist the hose on, use a heavy object or large rock to keep it in place. 

Open the Valve

Next, open the valve of the black tank. This allows the tank contents to flow through the hose and down the drain. Once you no longer hear the sound of running water, close the valve. 

Clean the Hose

Ensure you close the valve all the way. Then, detach the hose from the pipe. With a water hose specific to wastewater, spray the inside of your sewer hose. 

Next, replace the cap on the end of your drain pipe. Finally, ensure your tank is ready by putting a few gallons of water down the toilet. It’s also a good idea to use a cleaning chemical at this point. 

Cleaning an RV Black Water Tank

Every once in a while, it’s a good idea to give your RV black tank a deep clean. It’s good to do this every six months or so and anytime you plan to put your RV into storage. In some cases, it’s a good idea to clean the tank more often. 

Dump the Tank

Follow the guide above to dump the tank. However, at the end of the process, keep the sewer hose connected. 

Spray It Down

Once you empty the tank, attach a water hose to the backflush port. DO NOT USE YOUR FRESHWATER HOSE. 

If your RV doesn’t have a backflush port, there are kits and pumps available to help you out. 

Then, run water through the backflush to remove debris caught in the tank. It’s a good idea to have a clear section of hose at the end of the sewer hose so that you know when the water runs clear. 

Put Everything Away

Once the water runs clear, turn off the faucet, remove the hose, close the valve, and remove the sewer hose. As noted in the dump guide, be sure to clean the sewer hose before you put it away. 

Remember to replace the cap on the drain pipe once you finish. Lastly, add water and cleaning chemicals to the tank to ensure it stays in good and ready condition. 

Plumbing System Repair

Whether you have an issue with your RV black water tank or another aspect of your plumbing system, have a professional take a lot. Occasionally, the tanks in your plumbing system develop cracks that cause leaks. This can leave you in a smelly situation out on the road. 

Before you put your RV into storage or as you get ready for a big trip, it’s a good idea to have trusted technicians inspect the rig to ensure it’s ready. At TX RV Repair Shop, we are happy to help you with a broad array of RV repairs. 

Before you hit the road, let us help you keep your rig adventure-ready!