How To Empty RV Holding Tanks

The majority of RVs have onboard holding tanks. These tanks collect water from your camper shower and sinks, as well as sewage waste from your toilet(s). When they fill up, you’ll need to know how to empty RV holding tanks. 

What Are RV Holding Tanks?

RV tanks are separated into gray, black, and fresh water tanks. Your gray water tank holds sink and shower wastewater, your RV black tank collects toilet wastewater, and your fresh water tank holds clean water for use in your kitchen, bathroom, and toilet(s).

Generally, the combined volume of your wastewater tanks is the same as your RV’s fresh water capacity, but the volumes of the gray and black tanks are rarely equal. The gray tank usually accounts for about 60% of your fresh water capacity, and the black accounts for the remaining 40%. 

So, if an RV’s fresh water capacity was 80 gallons, the gray and black water waste tanks would hold roughly 48 gallons and 32 gallons, respectively. 

Technician Tip: Check your RV owner’s manual for the exact capacities of your holding tanks. 

How To Empty RV Holding Tanks

Your waste tanks must be drained regularly. To do this, you’ll need to locate an RV dump site or a sewage connection at a full-service campsite. Fortunately, you can use the same sewer hose connection to dispose of your gray and black water at a campsite or a dump station. 

At a full-service site, you can hook up your sewer connection as soon as you arrive, but you should keep your tanks closed until they are at least three-quarters full. That way, liquids will help flush solids when you open the handles, reducing the chances of a clog. Never leave your black tank handle open continuously when camping with full hookups. 

Don’t make this any messier than it needs to be. For starters, use RV-friendly toilet paper to avoid clogs and keep this process flowing smoothly. Before emptying your tanks, make sure you have rubber gloves and double-check that your sewer hose is in good condition. These tips for caring for an RV sewer hose should prove useful. 

Now let’s look at the full procedure of dumping your RV holding tanks.

Step 1: Find the Sewer Hookup

Before you pull into a campsite or dump station, locate the sewer hookup. Its exact location will dictate how you position your trailer. In most campsites, the sewer hookup is on the right side of the parking pad. This allows you to back in and place your holding tank outlets as close to the hookup as possible.  

Dump stations make things easier because you can drive right up next to the hookup. Still, you must make sure the sewer hookup is on the correct side of your trailer when you pull in. 

Keep in mind that your sewer hose should easily reach the hookup. Overstretching a sewer line can lead to cracks or breaks that will definitely upset your campground neighbors. 

Step 2: Connect a Hose to Fresh Water

Before you handle your sewer hose, connect one end of a water hose to a fresh water supply. You’ll eventually need potable water for clean-up after your tanks are empty, but it’s a good idea to connect your hose now so it’s ready if you wind up with a little bit of a mess in this process. 

If the campsite you’re using has a splitter on the water connection, keep your RV connected to city water and attach a second hose for dumping. If yours doesn’t, disconnect your city water hose and connect a separate hose for dumping. Most dump stations also have a water hose available for cleaning purposes. 

Technician Tip: Always use separate water hoses for getting clean drinking water in your RV and for dumping your waste tanks.

Step 3: Put On Personal Protective Equipment (PPE)

Prior to handling anything related to RV waste, pop on a pair of disposable gloves. Reusable rubber gloves are also a more environmentally friendly option as long as you sanitize them between uses. If you are sensitive to smells, there is no shame in donning a protective mask during this process. 

Step 4: Retrieve Your Sewer Hose and Check the Fittings

Now, retrieve your sewer hose from its storage compartment and check to make sure the sewer hose fittings on either end are secure. At one end, you’ll find a 90-degree connector that attaches to the sewer hookup. On the other, you’ll find a straight connector with a bayonet fitting that attaches to your holding tank outlet. 

Visually inspect the hose and fittings to make sure there are no holes or cracks present. 

Step 5: Connect Your Sewer Hose and Use a Sewer Hose Support

Next, place the 90-degree connector in the sewer hookup. Some sites may have a cap that must be removed first. Ideally, the hookup is threaded so you can screw your 90-degree connector in to secure it. If it doesn’t, lean a flat rock on top to keep it in place. 

At the opposite end, check that the handles that control the outflow of your gray and black water tanks are pushed completely closed. Then, remove the cap on the septic tank outlet and install the bayonet fitting. 

Technician Tip: A small amount of waste can drip out of the outlet even when both tank handles are closed. Place your sewer line under the outlet to catch anything that does drip. If an excessive amount of waste leaks in the space between your sewer outlet cap and the valves for both tanks every time you dump, you may need to have your valve seals checked and serviced. 

When hooking up in a campground for multiple days, it’s best to use a sewer hose support instead of allowing the hose to rest directly on the ground. Place the support underneath your sewer hose to create a natural gradient that improves refuse flow and reduces the chance of a clog. 

If you need to save time, you don’t need a sewer hose support at a dump station. If you don’t, waste is more likely to accumulate in the hose when you elevate it to finish the dumping process.

Step 6: Identify Black Water and Gray Water Handles

Locate the two T-shaped handles on the plumbing running to your holding tank outlet. These handles control the outflow for your gray water and black water holding tanks. On some RVs, the handles will be color-coded (gray and black) to signify which tank they control. 

If your handles aren’t color-coded, the handle on the smaller pipe controls your gray water tank, and the handle on the larger pipe is for dumping your black water. 

Step 7: Dump Black Water First, Then Gray Water

When dumping the tanks, start with the black water. Then, you effectively use gray water to rinse black water from your sewer hose. Open the handle for your black water tank slowly until you hear waste flowing through the hose. 

Then stop. Don’t pull the handle all the way out at first. This relieves the initial pressure while you check that everything is emptying as expected. Visually confirm no leaks are present before you open the handle all the way. 

It may take a few minutes for your black water to drain completely but DO NOT walk away. Remain close so you can quickly push the handle closed if something goes awry. 

When you no longer hear black water emptying, open the handle for your gray water tank. Again, pull the handle out slowly and only partially at first to relieve the initial pressure. Then, pull the handle all the way open and wait for the tank to empty. Leave the handle for your black water tank open during this process to allow any remaining contents to continue draining. 

Step 8: Perform a Preliminary Fresh Water Flush

When you no longer hear black or gray water draining, push the handles for both holding tanks closed. If your sewer hose is equipped with a clear 90-degree connector, you can also visually confirm that waste is no longer draining from your tanks before closing the handles.

Leave your sewer hose connected and head inside. If you’re connected to city water, open the faucets in your kitchen and bathroom sinks for 30-60 seconds. 

While the water is running, partially depress the pedal on your toilet until the water reaches the fill line inside. Then, depress the pedal completely to empty water into your black water tank. Repeat four times. 

When using a dump station, you can use water from your onboard tanks for this preliminary flush. If you want to keep your freshwater tank full, you can fill a water jug and pour it down your sinks and toilets. 

The idea is to partially fill your tanks with fresh water to detach and rinse anything that didn’t get emptied in the first cycle. Then, go back outside and open the handles in the same order as the first time (black first and then gray). Let contents drain completely.

Step 9: Use Your Black Tank Flush (if Equipped)

Many motorhomes and travel trailers are equipped with a black water tank flush mechanism. This is located on the outside of the camper near connections for your city water and cable/satellite hookups.

To use it, you’ll need that garden hose you connected earlier. Connect the disconnected end to the black tank flush inlet. Make sure the handle on your RV’s black water tank is pulled completely open. 

Then, open the handle on the water spigot to run water into the flush mechanism, through your black water tank, and out your sewer hose. Open the spigot partially at first to check that everything is working properly. 

When you’re satisfied it is, open it all the way and allow water to run through your black water tank and sewer hose until they are clear. Then, turn off the water and disconnect the water hose from the flush inlet. Water will continue to drain out of your sewer hose for a short period after you disconnect. 

Step 10: Close The Handles and Clear The Hose

When you don’t hear anything running through your sewer hose anymore, push the handles for both tanks closed. Now, this is a quick reminder to put protective gloves back on if you removed them for some reason earlier in the process.

Starting at the bayonet fitting, lift the hose and shake it gently to move any remaining particles down and towards the outlet. Do this over the entire length of the hose to remove as much leftover waste as possible. 

Step 11: Disconnect Your Sewer Hose

Now, it’s time to disconnect the bayonet fitting and replace the holding tank cap. Twist to remove, but make sure you keep the open end pointing upward as you replace the cap. Keep the bayonet fitting elevated as you gently shake the hose and walk it away from your trailer. For now, leave the 90-degree connector in place in the sewer hookup. 

Step 12: Rinse, Pack Up, and Wash Up!

Not all trailer owners do this, but there’s nothing worse than handling a sewer hose that still contains remnants of you-know-what. So, before you detach your 90-degree connector from the sewer hookup at a campsite or dump station, grab your water hose and run a little more fresh water through it. 

Shake and swirl the hose–keeping the bayonet fitting pointed upward–to clean it out as completely as possible. 

Now you can disconnect the 90-degree connector on your sewer hose and coil it up. Place it back inside your holding tank compartment along with your sewer hose support. Close and secure the cap on the sewer hookup at the campsite or dump station (if applicable). If you choose disposable gloves, you can dispose of them now. 

While your water hose is still attached, rinse your reusable gloves if you use them. If not, it’s also a great time to rinse your hands with soap and water. Then, disconnect your fresh water hose and store it in a separate compartment if you want to avoid contamination. 

Also, double-check that the cap on your holding tank outlet is secure before closing and locking your holding tank compartment. 

Additional Tips For Emptying RV Holding Tanks

Here are a few more pointers to keep in mind regarding hooking up and dumping RV waste tanks: 

• At campsites, tank handles should be closed until you’re ready to empty your tanks. 
• It’s okay to leave your sewer hose connected for multiple days, but leaving the tank handles open increases your chances of a clog because liquids will empty while solids will remain in your tank or the hose.
• If you drop RV chemicals into your black tank, it will need to be at least 3/4 full for chemicals to adequately break down the solids before emptying the tank.  
• Install a clear 90-degree connector to visually make sure you’ve fully emptied tanks.
• Fill your RV toilet bowl to ¾ of its capacity before emptying tanks to reduce odors.
• Utilize a tank treatment every few weeks to reduce odors and break down debris that can accumulate in your RV’s septic system.

What About RV Macerator Pumps?

Today, options are available that change the way RV sanitation systems operate. Macerator pumps, for one, reduce the viscosity of what was considered normal black tank waste and allow it to be disposed of via a 1″ hose, even uphill.

So, what exactly are the main advantages of this feature? Well, there are many! Firstly, you can empty your black tank, and gray tank for that matter, in a household toilet provided it is within the reach of the discharge hose. 

Unlike all other RV sewage systems, macerator pumps don’t rely on gravity to move the liquid. They push it and can propel its output above its own elevation. They also boast the easiest and cleanest operation available.

So, unlike in the game of poker, when it comes to RV holding tanks, a flush beats a full house. Of course, there’s more to RV toilets than just emptying the holding tanks. Check out our tips on how to use an RV toilet.

Do you have any fun (or not-so-fun) stories about your first time emptying your RV’s holding tanks? Leave a comment below!