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How Does Your RV Bathroom Work?

March 25, 2020

How Does Your RV Bathroom Work?


  1. There are major differences between an RV bathroom and a home’s bathroom! RV bathrooms use holding tanks to store waste until you are ready to dump; home bathrooms bypass this step and send waste directly to the septic system. RV holding tanks can require more care than a traditional home bathroom.
  2. When using your RV bathroom, you must only allow certain items to enter your tanks. Gray tanks can malfunction if large amounts of grease and fat are allowed to enter via the drains. In the same vein, you should only allow human waste and toilet paper into your black tank.
  3. Follow The Unique Method to properly care for your RV black and gray tanks! See the detailed steps below for specifics about preventative care.

For many RVers, owning a motorhome can be an extension of your home life. And for those of you that are full-time RVers, it is your home life! But, especially if you're new to RVing, you should know that despite your RV’s luxuries, there are still some major differences between your RV bathroom and your home's bathroom! In this article, we will discuss the biggest differences you should remember, focusing on plumbing, ventilation, what you can flush, and preventative care.

In terms of plumbing, probably the biggest and most glaring difference between your RV’s bathroom and your home’s bathroom is that waste is stored in a holding tank in your RV. Although seemingly trivial, this can present problems if it isn't handled correctly.

Let's dive into what makes RV bathrooms unique!

RV Bathrooms vs Home Bathrooms

RV bathrooms use a combination of holding tanks, plumbing, and ventilation to keep the waste contained until you dump the tanks into a sewer or septic system. Alternatively, in your home bathrooms, the waste is flushed down the toilets or drains and goes directly into the sewer or septic system without ever being held in a tank.

There are two types of holding tanks used in your RV bathroom: (1) a gray tank for your sinks, shower, and bathtub and (2) a black tank for your toilets. The two types of tanks are kept separate because of the different kinds of waste. 

In many cases, the only thing separating you from your stinky black tank is the toilet valve (i.e., the flap inside your toilet bowl) and the water you keep in your toilet bowl. In many cases, these two odor barriers simply aren’t enough, and you will have to supplement with a bacteria-based, high-quality holding tank treatment to keep odors down. (We give some additional tips on keeping odors down in The Unique Method, which we'll talk about more below, and our guide to fixing odors!)

When it comes to your gray tank, there is one big thing to keep in mind. Because you mainly use the water in your RV for meal preparations, cleaning your hands, and bathing, it is very easy to have grease build up inside your gray tank, which will produce odors. In other words, it’s not just your black tank that can be stinky! Keeping your gray tank odor-free has a whole lot to do with what you allow down your sinks and drains (see below).

Both the gray and black tanks in your RV have ventilation systems that pull air through the tank and release it out of the top or side of the RV. For the most part, the ventilation process occurs while you are driving. Therefore, even though your tanks might be venting off while you’re parked, they may need a little to keep odors in check when you have stopped for the night/week/month/year. 

As we mentioned above, both tanks can get stinky. We will talk about preventing these problems in a second. First, we need to go over what kinds of waste should be allowed in your holding tanks.

What You Should Allow in Your RV Holding Tanks

As you have probably figured by now, it can be very easy to have problems with your holding tanks! A big piece of that problem-puzzle has to do with what you allow in your drains and toilet. So let's go over what exactly is allowed inside your holding tanks! (For a deeper dive into this topic, please see our article, What to Flush!)

Gray Tanks

Believe it or not, if used incorrectly, gray tanks can sometimes cause bigger issues than black tanks! Here’s one huge way to prevent it: never allow food waste down your drain. The more you can minimize food waste from getting into your gray tank, the better off you’ll be! Many people use an in-drain strainer, which can be very helpful. Another thing to be aware of are the greases from food and soaps. As mentioned above, grease and fat can easily build up on the walls of your gray tank. This is often the cause of the two most common issues with gray tanks: (1) odors and (2) misreading sensors. The solution? Keep grease and fat out of your drains!

You also should be performing a yearly deep clean of your gray tank, which you can read more about here!

Black Tanks

You should only flush human waste and toilet paper down your RV’s toilet. These are the only two items that you should allow to enter your black tank, because anything besides human waste and toilet paper could potentially cause clogs and back-ups. The only exception to this rule is an RV toilet cleaner that has been specially designed for use in a RV holding tank. 

As we alluded to above, a holding tank treatment is a product used to control all of the ramifications of storing waste. A high-quality holding tank treatment will do two things: (1) break down waste and (2) control odors. For many people, an RV toilet cleaner is an integral part of their RV maintenance, so you should make sure that you choose the right product for your needs! We recommend RV Digest-It and Unique Holding Tank Enhancing Toilet Cleaner. These are superior products that will boost the bacteria colonies inside your holding tank!

Water is another key to success with your holding tanks. It is extremely important to use plenty of water in your black tank. By using an ample amount of water, you will maintain a consistent water level that will allow your holding tank treatment to reach all of the waste in your tank. On top of that, water creates a barrier between the waste in your holding tank and the open air, helping prevent strong odors. 

Here is how we recommend using water in your black tank:

  1. Always keep your black tank valve closed! Unless you’re dumping your tank, your black tank valve should always be closed.
  2. Use plenty of water! We recommend flushing your RV toilet for 10 seconds after each use.
  3. Create a water barrier! Keep several inches of water in your toilet bowl to prevent sewer smells from seeping into your RV.

Water use in your gray tank is fairly straightforward. If you are camping on full hook-ups, create a water barrier in your waste hose line. You can create a barrier by making a kink in your waste hose—similar to a "p-trap" in your household toilet. Your gray tank valve should be left open at all times when you are camping on full hookups to prevent grease build up and potential odors from food waste.

Please note that some states have laws that require you to keep your waste hose off the ground. Make sure you abide by all local laws.

With all that out of the way, you might be asking why you should close your black tank valve but leave your gray tank valve open? Well, let’s jump into preventative care for your RV holding tanks and, in the process, answer that question! These points come directly from The Unique Method—a proven wastewater treatment system designed to make your RVing experience way easier!

Preventative Care

For Black Tanks
  1. Always keep your black tank valve closed! This keeps liquids inside your holding tank, allowing for a waste digesting holding tank treatment to control clogs and odors.
  2. Use a high-quality waste digesting holding tank treatment! We recommend RV Digest-It
  3. Keep an eye on your holding tank temperatures! Odors can get out of control in high heat. Treat this with cold water or ice and/or use an odor eliminating tank treatment.
  4. Use plenty of water! Flush your RV toilet for 10 seconds after each use and fill your toilet bowl halfway with water after each use.
  5. Flush your holding tank often! No holding tank is mounted perfectly level. We recommend flushing every 3-5 dumps to make sure no residual waste buildup causes odors.

If you follow these guidelines, you will take an active position to prevent odors and clogs in your black tank! Take control of your holding tanks by following The Unique Method—the best waste treatment system out there! Touch or click here to learn more. 

For Gray Tanks

Camping with Full Hookups
  1. Keep you gray tank valve open when possible! This creates a water barrier inside your hose in the form of a “p-trap.”
  2. Don't allow food waste down your drain, especially greases and fats from cooking!
  3. Use a high-quality tank cleaner when cleaning your tank! We recommend Unique Tank Cleaner to treat grease build up and foul odors.
  4. Treat with an odor eliminating tank treatment if you get odors in high heat! We recommend Unique Tank Odor Eliminator
Dry Camping
  1. Keep your gray tank valve closed! It is illegal in most states to allow your gray water to open dump onto public lands.
  2. Never allow food waste down your drain!
  3. Use a high-quality waste digester to control odors and grease build up! Grease builds up faster when you keep water contained, so it is important to use a tank treatment to control potential odors. We recommend RV Digest-It.
  4. Treat with an odor eliminating tank treatment if you get odors in high heat! We recommend Unique Tank Odor Eliminator

The biggest reason we say to keep your gray tank valve open is because (ideally) you aren't allowing large volumes of solid waste into your tank. This means that only liquids will trickle out of your tank and into the sewer. By keeping your gray tank open when possible, you will help prevent odors. If you were to leave your black tank valve open in the same way, you would consistently experience clogs because of the volume of solid waste that would back up when the liquids trickle out.


As you can see, there is a world of difference between your RV bathroom and your household bathrooms! Your RV bathroom might need a little extra work to keep things running in tip-top shape, but we think it’s worth the effort! Start building your holding tank habits now, and you'll start to turn your house on wheels into a home on wheels! 

Please feel free to contact us at anytime if you have any questions. We are happy to help! Email us to get in touch with our customer support team.

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