RV Black Water Tank: 6 Things You Need to Know (2023)

Your RV’s black water tank is a very important piece of equipment: it’s the tank under your rig that holds the waste water from your toilet. While where everything goes when you “go” is no one’s favorite thing to think about, it’s part of what makes RVing so much more convenient and enjoyable than regular car travel or tent camping — no more relying on rancid pit toilets at the campground!

If you want to learn even more about your RV’s black water tank and about maintaining and repairing your RV in general, NRVTA’s program is perfect for you. Click here and use code RVSHARE for 5% off all courses.

The RV Owners home study course comes in two options.

Online & USB

  • The USB version is $297 and includes booklets, a tweaker screwdriver, and a USB Drive with all of the HD videos. It also includes a copy of the online version. This is perfect for RVers who may not have access to good wifi or likes to have a physical copy.
  • The Online version is $197 and includes all of the same videos laid out in chapters using our online portal. It’s good for RV owners who have good wifi, don’t want to wait on UPS, or like to keep everything digital.

Of course, if you want to keep your RV’s black water tank working properly and whisking away your waste, there are a few things you absolutely need to know about how it works.

Here are six things to know about your RV septic tank… before you go.

RV Black Water Tank: 6 Things You Need to Know (1)

1. What is an RV Black Water Tank?

Most self-contained RVs have two types of waste tanks on board: a gray water tank and a black water tank.

A gray water tank collects the water that goes down the drain of your RV shower and sinks. It is the presence of soap residue and dirt that give this wastewater its name and gray-ish look. For more on grey tanks, check out this article.

(Video) 6 Things You Should Never do with an RV Sewer Hose

What we’re concerned with is the other one: the black water tank, which catches the wastewater from your RV toilet. It’s called a black water tank for obvious reasons, and you probably aren’t too keen to see just how black the water from this tank can be.

This tank is what allows you to use your RV’s onboard facilities without having to worry about being constantly hooked up to a sewer connection. That said, a city sewer is the only place you should ever dump your RV’s portable black water waste tank.

The black water tank collects both liquids and solids, so caring for it is a bit different than your gray tank. In addition to human waste, the RV black tank also collects water used to flush the toilet, and of course, toilet paper. Which, by the way, should be RV-specific toilet paper, which is more easily degradable and less likely to clog your rig’s sensitive plumbing system!

2. How do I Clean my RV Black Water Tank?

Knowing what your black water tank holds, the next logical question to ask is: how the heck do you keep it clean and odor-free? What kind of RV black water tank cleaning chemicals are the best? Should you add bleach?

Fortunately, the availability of commercial chemicals and deodorizers makes it pretty simple to maintain your black tank on a regular basis.

At the start of your camping trip, you should add a dose of RV black water tank treatment, which may come in liquid form (like Aqua-Kem) or in Tide-Pod-like packets (such as these). Be sure to add in about a gallon of water, as well, which helps the chemicals do their job.

Along with keeping tank odors down, these chemicals also have the ability to break down solid waste and toilet paper. That makes for a much smoother process when it comes time to dump your tanks — which we’ll get to in just a minute.

In addition to maintaining your black water tank with these cleaning solutions, it’s also important to deep clean your tanks on a regular basis, perhaps between camping trips or before putting the rig into storage.

The materials used for a deep clean vary among RV owners, but the method usually stays the same: drain your waste tank completely before filling it ¾ full with fresh water and either a small amount of bleach or Pine-sol, or laundry soap. Then, drain the tank, before filling it ¾ full again with fresh water. Repeat this last step until the water runs clear.

(Video) First Time Camper Series: Understanding your RV Holding Tanks

Finally, if you do get a clog in your RV black water tank — which can happen, even if you use the right chemicals and toilet paper — there are a variety of methods for getting things back on track. You might try ice cubes or boiling water, for instance; click here for the full details on how to deal with a clogged RV potty!

RV Black Water Tank: 6 Things You Need to Know (2)

3. How Often Should You Dump and Empty Your Black Water Tank?

When you’ve gotta go, you’ve gotta go — and the same can be said for your RV! Of course, the exact frequency with which you need to dump and empty your tanks will vary, just as it does with how often you need to go.

For instance, if you’re traveling alone and frequently spending days outside of the RV adventuring, you might be able to last a week or longer without dumping the tanks. On the other hand, if you’re camping with a big family (or traveling in an RV with small tanks), you may find yourself emptying the tank every other day or so.

Most self-contained RVs have a sensor that tells you how full each of the tanks are. This includes the black water tank as well as the gray water and potable water holding tanks. However, with some smaller trailers, like Casitas, there’s no sensor. Rather, you just sort of…figure out that it’s time as the water level rises.

At the very least, you should dump and empty your black water tank after each camping trip, as you don’t want to store your RV with wastewater in the tanks! In fact, you’ll want to thoroughly flush your system — which we’ll talk about in the next section. But first, let’s go into how to dump the black tank on your RV, step by step.

Looking for a dump station nearby? See this page!

4. How do I Dump my Waste from my Black Water Tank?

To dump your RV’s black water holding tank:

  1. First, put on a pair of rubber gloves. Better safe than sorry!
  2. Hook up one end of your sewage drain hose to the black tank valve on your RV. Secure the other end of the hose to the valve at the sewer line or dumping station.
  3. Pull the valve to empty the black tank, allowing it to drain completely.
  4. Flush the black tank with water to clean it. Depending on your setup, you may be able to do this using the water from your gray water tank.
  5. Drain all of the water from the tank.
  6. Repeat steps 2-4 with the gray water tank.
  7. Close the valve and remove the hose from your RV water tank.
  8. Rinse off the inside of the hose before disconnecting from the sewer connection or dumping station.
  9. Remove the sewer hose and properly store it.

5. What is RV Black Tank Flushing?

Some RVs have a built-in RV black tank flush system, which allows you to connect a hose directly to an inlet valve to essentially power wash your tank. This makes it super simple to ensure your tanks are sparkling clean.

(Video) RV Holding Tanks - Learn about the Grey & Black Water Tanks

When using the flush valve, you’ll want to follow your manufacturer’s instructions to ensure you’re using it correctly. Most guides suggest you leave the black tank valve open, so that water doesn’t back up and end up flooding your RV through the toilet!

If your RV doesn’t come with a built-in black tank flush system, it is possible to install one aftermarket. This type of after-market option comes in many shapes and sizes. Some can be attached to the dump pipe and others require drilling a hole in your RV black water tank.

Lastly, if you don’t have a manufacturer’s tank flush valve, and you don’t wish to add one to your tank yourself, you will need to employ a more manual method of RV black water tank cleaning.

One of the more popular options, for an RV black tank cleaner, is to utilize a garden hose extension called an RV holding tank rinser that goes down the toilet. This rinser is designed to spray water in multiple directions, in order to clean debris and tissue from the sides of your RV black water tank.

Other owners also utilize the ice cube method mentioned in this post on cleaning your RV’s black water holding tank sensors. Add in some mild detergent, like Dawn or Joy, and you’ve got a great homemade black water flushing process!

RV Black Water Tank: 6 Things You Need to Know (3)

6. Portable RV Waste Tanks

If you camp in the same spot for long periods of time without sewer hookups, you may find it necessary to take advantage of a portable RV waste tank.

These waste tanks allow you to empty the contents of your black and grey water tanks into an external tank, which you can then transport to a dump station. RV portable waste tanks usually have wheels and a handle, so they can easily be pulled across the campground for dumping.

It is important to realize that if you use a portable RV waste tank, you should take the same care to clean and flush it, as you do with the onboard RV black water tank.

Frequently Asked Questions about RV Black Water Tanks!

To close out this post, a few frequently asked questions — and their answers!

(Video) RV 101® - How To Use RV Black and Gray Water Holding Tanks - New RV Training

What’s the difference between gray water and black water?

As mentioned above, gray water is the wastewater that comes from your sink taps and shower — whereas black water is the waste that comes from your toilet. See our guide on RV water tanks and RV holding tanks for more.

How accurate are the black tank monitors?

The accuracy of your tank monitors depends on how often you clean them! Here’s how to clean your RV’s black water tank sensors.

Best practices for black tank dumping?

As mentioned above, always ensure you’re dumping your holding tanks into a city sewer connection made specifically for that purpose — never out onto the ground or into a street sewer a la Christmas Vacation!

It’s also a good idea to keep your valves shut and wait until the tanks are full, or nearly full, to dump, as then you have the help of gravity and a lot of water to wash the icky stuff through the hose.

Keeping tanks closed until full also helps prevent clogs. You see, without water constantly sitting at the base of the tank, your waste’s odour will be more pungent. Plus, certain things may stick to the bottom of your tank, making them more difficult to remove (if you know what we mean…).

What are some black tank maintenance tips?

Always use specially formulated RV holding tank chemicals to ensure your tanks stay odor-free and that waste is broken down quickly and effectively. While you can use mild dish detergent or ice to clean your tanks more thoroughly, avoid using harsher substances, like antifreeze, which can dry out the seals and ruin your sewer system.

Does my toilet use affect anything?

Your RV toilet isn’t like the one you have in your home. Flushing trash, feminine products, and traditional toilet paper can lead to a clog in no time, and it’ll be no fun to clean up. Treat your toilet with care and only flush the bare necessities. That way, it’ll be there for you for many camping trips to come.

Do I have to dump my own black tank?

Maybe after reading this, you don’t feel like messing around with the RV waste tank at all. If the idea of buying and going camping in an RV is sounding less and less appealing, don’t abandon your road tripping dreams just yet.

Although it’s still considered a relatively new service, an increasing number of campgrounds are now offering “honey wagon service,” where someone comes around to dump your tanks for you, typically for a fee. Many KOA campgrounds now offer this service to guests as another perk.

(Video) Dumping your RV's Black and Grey RV Water Tanks

Dealing with your RV black water tank is definitely one of the more unpleasant areas of using an RV. However, the comfort and privacy that having an RV toilet on board affords you and your family is one of the biggest advantages to having an RV. Understanding your RV black water tank, and how to clean it, will give you years of comfort and odorless enjoyment.

This post contains affiliate links. RVshare may receive compensation if you make a purchase after clicking on a product or service link.


How much water should you put in your black tank before use? ›

Keep Enough Water in Your Tank

Your holding tanks should always be at least ⅓ of the way full with water. So, after you dump and clean, fill the tanks with water until they're at least ⅓ of the way full. This is especially important for the RV black tank.

How long should you run your black tank flush on your RV? ›

This ensures the water is reaching the spots that the built-in sprayer can't get to. Pull the black water tank valve. Let the water run for 10-15 minutes, but don't leave it unattended.

How often should you drain the black tank in a RV? ›

How often you need to empty your tanks is relative. If you are traveling with a large number of people, you may need to empty your tanks every other day. If it is just you and your spouse, once a week may be enough. A general rule of thumb is to wait until your tanks are about two-thirds full before emptying them.

Should you leave some water in black tank? ›

The addition of fresh water is very important as you never want to have a dry black tank. Never leave your black tank open when connected to a campground sewer hookup. There's no pretty way to explain this: The liquid waste needs to build up with the solid waste in a black tank in order for it to properly flush out.

Should I leave a little water in my RV black tank? ›

Dump your black tank.

They think it's ok to leave the wastewater in there during the week until they have a chance to dump it. This is definitely not recommended because sitting waste will always have the potential for developing clogs, odors, and misreading sensors.

Can you put Dawn in RV black tank? ›

One of the best parts about using Dawn dish soap in RV black tanks is that it's an environmentally-friendly soap. It doesn't contain phosphates and can be broken down by bacteria. This means that it's a safe and biodegradable soap to use, even if you're cleaning/dumping your tank in a strict or natural environment.

Do you need to winterize the black tank flush? ›

A black water flush system is entirely separate from the rest of your water system. This is an often overlooked step in the winterization process for RVers. Because you'll need to pump the RV-safe antifreeze into the black tank flush components, you'll need an antifreeze hand pump to get the job done.

How do you get rid of the poop pyramid in RV black? ›

To eliminate a poop pyramid, you need to get water into your black tank. The first thing you should do is close the black tank valve and get as much water into the black tank as possible. If the poop pyramid prohibits you from putting water into the tank, get some tank cleaner to pour down into the sewer drain.

Can I put Pine Sol in my RV black tank? ›

Pine-sol is for odor and the Bath Beads are to keep the tanks slippery as well as to lubricate the seals. You can also mix the water and bath beads in the gallon jug and only add pine-sol in the tank if needed for odor.

Can I put vinegar in my black tank? ›

Vinegar is safe to flush into the black water tank, but it works better when you include baking soda. Baking soda is broken down by the acid in vinegar. This releases carbon dioxide gas that can help remove dirt from the surfaces being cleaned. For the best result, flush this mixture with hot water.

How do I know when my black water tank is full? ›

The only way to tell for certain how full a black tank is, is when it backs up into your toilet. When the contents of your toilet won't drain, it's almost always because the tank has reached its full capacity.

Can you travel with black tank full? ›

Should You Travel With Your Tanks Full? For black and gray tanks, the answer is a clear “no.” But you may want to have a little water in there for cleaning purposes.

Does shower water go into black tank? ›

Sinks do drain into black tanks sometimes. It is by design. Showers only drain to gray.

Do you empty gray or black tank first? ›

Dump the black water tank first, then the gray tank. Dumping the gray tank last helps flush out the sewer hose. After you dump both tanks, thoroughly flush out the tanks. Some RVs have a built-in system for flushing.

How do you keep a black tank from smelling? ›

How To Get Rid Of Awful Black Tank Smells
  1. Start with fabric softener. Begin your troubleshooting by simply adding two capfuls of liquid fabric softener to the tank. ...
  2. Fill the bowl. ...
  3. Close the valve. ...
  4. Check the vent. ...
  5. Pull out the water hose. ...
  6. Try ice and soap. ...
  7. Dump in some water softener. ...
  8. Resort to bleach.
25 Apr 2019

How do you winterize a black water tank? ›

Clean and flush your black and gray water tanks, drain the fresh water tank completely, then close the drain valves. Pour one quart of special RV antifreeze into the gray and black tanks to protect the drain valves and seals. Do this through all sink and shower drains—you want antifreeze in the pipe traps as well.

How do you clean a black tank in the winter? ›

For the best deep cleaning results, dump your tanks and remove debris as you would normally, and then drain the tanks completely. After tanks are drained, fill them around ¾ of the way full and add bleach (two cups should do it in most cases – make sure to keep the toilet lid closed to avoid harmful fumes)

How long does it take to empty a black water tank? ›

It shouldn't take you more than 10 minutes to dump out and do a quick flush with the tank flush or a bucket if others are waiting such as on a Sunday afternoon after a busy weekend.

What does Borax do in black tank? ›

The Borax detergent helps control odor and cleans the tank. The water softener makes the water softer and more slippery, preventing waste from sticking to the walls of the waste tank. I've been using this combo while living and traveling full-time our RV for the last four years with good results.

Can you put vinegar and baking soda in RV toilet? ›

The drains on our RVs can get gross and nasty quickly. The best way to relieve that is to pour half of a box of baking soda down the drain and then follow it with vinegar, allowing it to foam up. After it's settled, pour more vinegar in the drain and repeat until all of the baking soda is gone.

Can I use toilet bowl cleaner in my RV toilet? ›

The general consensus, based on recommendations from most RV toilet manufacturers, is that you should avoid the use of harsh or abrasive cleaners. That's because they want to be sure these products don't damage the bowl, the toilet's blade valve and seal, and/or the black water tank.

How do you prepare a black water tank? ›

The most basic procedure for cleaning your black tank goes like this.
  1. Drain your tank.
  2. Remove any buildup in the system thoroughly.
  3. Add some water to the tank.
  4. Add a good black water treatment.
14 Feb 2020

How do I prepare my RV black tank? ›

RV Black Tank Maintenance
  1. Treatments and Cleaners. In order to properly clean out your RV's tank, you will also need a treatment of some sort. ...
  2. 1) Dump Your Tank. ...
  3. 2) Remove Buildup by Flushing Your Tank. ...
  4. 3) Add Water. ...
  5. 4) Add Treatment or Solution. ...
  6. 5) Rinse. ...
  7. Knowing the Time and the Place. ...
  8. Toilet Paper.
11 Dec 2020

How long does a 40 gallon black water tank last? ›

Some RVers report that a 40-gallon black tank will last two people about 10 days before needing to dump, but again, this all depends on toilet paper usage, water usage, and the number of people using the water systems. Another technique is to always dump when your tanks are two thirds or three quarters full.

How long does it take to fill black water tank? ›

We (two adults) also start out with 4-5 gallons of water to prevent the black pyramid from building up. In 5-6 days, the 39 gallon tank looked to be maybe half full. I added water before dumping. Three of us fill ours up in about 48 hours.

Does shower water go into black tank? ›

Sinks do drain into black tanks sometimes. It is by design. Showers only drain to gray.

Can I put Pine Sol in my RV black tank? ›

Pine-sol is for odor and the Bath Beads are to keep the tanks slippery as well as to lubricate the seals. You can also mix the water and bath beads in the gallon jug and only add pine-sol in the tank if needed for odor.

How do you get rid of the poop pyramid in RV black? ›

To eliminate a poop pyramid, you need to get water into your black tank. The first thing you should do is close the black tank valve and get as much water into the black tank as possible. If the poop pyramid prohibits you from putting water into the tank, get some tank cleaner to pour down into the sewer drain.

Can you travel with black tank full? ›

Should You Travel With Your Tanks Full? For black and gray tanks, the answer is a clear “no.” But you may want to have a little water in there for cleaning purposes.

How can I make my black tank last longer? ›

Use an “RV Swivel Stick” (see it on Amazon) to break up the solids and flush them out. Use this each time after you have dumped the black tank to keep it free of build-ups. Make sure to use plenty of black tank enzyme to prevent solids from building up more.

How much borax and Dawn do I need to clean my RV tank? ›

You can also add 1 cup of the original “blue” Dawn dishwashing detergent. Or, add 1 cup of eco-friendly laundry detergent to the black tank when you add the water softener. This helps to further clean and deodorize the tank. Many RVers also include ¼ cup Borax to the black tank along with the detergent.

How long can you wait to empty black tank? ›

However, experts we've talked to agree on one thing: Empty your black tank within a week of it being full. And, if you're planning on going camping for several weeks, you might want to empty it more often—just to be safe. Also, use the appropriate toilet paper to avoid clogging up your black tank.

How big should my black tank be? ›

Size and capacity also depends on the size of your RV or camper, but on average, the black tank will hold between 18 and 64 gallons. Fifth wheels usually have the largest black tanks, which can hold 39 to 88 gallons when full. The black tank in Class A RVs usually have capacity for 31 to 51 gallons.

Do you need to use RV toilet paper? ›

Many new RVers wonder whether it's really necessary to use RV toilet paper. The truth is yes. You do indeed need to use quick-dissolving RV toilet paper. If you don't have tissue that's safe for RV use, you shouldn't flush it into your RV's sewage system.


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