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How Does Your RV Bathroom Work?

March 12, 2019

How Does Your RV Bathroom Work?

For many RVers, owning a motorhome can be an extension of your home life. For those of you that full time, it is your home life. Despite the luxuries your RV has, there are some major differences between your RV bathroom and a household water closet. In this article we will discuss the biggest differences you should remember. We will talk about plumbing, ventilation, what you can flush, and preventative care. 

Probably the biggest and most glaring difference between your RV and home bathroom plumbing is that in your RV the waste is stored in a holding tank. This aspect alone, although seemingly trivial, is the biggest and most obvious difference and that 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 waste contained until you dump the tanks into a sewer or septic system. 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 holding tanks used in your RV bathroom. A gray tank for your sinks and shower / bath tub, and 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 (the flap INSIDE your toilet bowl) and the water you keep in your toilet bowl. In many cases this isn't enough and you will have to supplement with a holding tank treatment to keep odors down. 

When it comes to you gray tank, there is one big thing to keep in mind: Because you mainly use the water in your RV to for meal preparations, cleaning your hands, and bathing, it is very easy to have grease build up and odors in your gray tank. So its not just your black tank that can be stinky. This has a lot to do with what you allow down your sinks and drains.

Both tanks have ventilation systems that pull air through the tank and release it out of the top or side of the RV. This process actually happens mostly while you are driving, so even though your tanks might be venting off when you are parked, it may take a little extra help 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 issues with your holding tanks and a big piece of this has to do with what you allow in your drains and toilet. Let's go over what is allowed to flush down your holding tanks.

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Gray Tanks

Believe it or not, gray tanks can sometimes be a bigger issue than black tanks if used incorrectly. First off, you should never allow food waste down your drain. The more you can minimize food waste from getting into your gray tank the better off you will be. Using an in-drain strainer can really help with keeping food out. Another thing to be aware of are the greases from food and soaps. Grease and fat build up on the tank walls of your gray water holding tank often cause most of the issues you encounter - odors and misreading sensors. Keeping grease and fat away from your drain will help you avoid these issues.

Black Tanks

With your black tank, human waste and toilet paper are the only things that should be flushed. Anything besides human waste and toilet paper could potentially cause clogs and back-ups. The only exception to this rule is an RV toilet chemical that has been specially designed for use in a RV holding tank. 

A holding tank treatment is a chemical that is used to control all of the ramifications of storing waste. A quality holding tank treatment will do two things, break down waste and control odors. Read this article to find out which one is right for you. For many, an RV toilet chemical is an integral part of their RV maintenance, make sure you choose the right product for your needs!

Water is another key to success with your holding tanks. With your black tank it is super important to use plenty of water. By using an ample amount of water, you will maintain a consistent water level that will allow your holding tank chemical to reach all of the waste in your tank. On top of that, it 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 Valve Closed - Unless dumping your tank, your black tank valve should always be closed.
  2. Use Plenty Of Water - Flush 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.

Creating a pea pee trap kink in RV sewer black tank sewage line hose to prevent sewer septic toilet gassesWater use in your gray tank is pretty straight forward. 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 there are different laws by state that require you to keep your waste hose off the ground. Make sure you abide by all local laws.

You might be asking why you should close your black valve but leave your gray tank valve open? Well lets get into preventative care for your RV holding tanks!

Preventative Care


For Black Tanks
  1. Always Keep Your Black Tank Valve Closed - This keeps liquids in your holding tank, allowing for a waste digesting holding tank treatment to control clogs and odors.
  2. Use A Quality Waste Digesting Holding Tank Treatment - We recommend RV Digest-It.
  3. Watch Your Holding Tank Temperatures - Odors can get out of control in high heat, treat with cold water or ice, and/or use an odor eliminating tank treatment.
  4. Use Plenty Of Water - Flush your RV toilet after each use for 10 seconds and fill your toilet bowl half way 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 build up is causing 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! Learn more about The Unique Method here.


For Gray Tanks

For Camping with Full Hookups

  1. Keep Gray Tank Valve Open When Possible - Create a water barrier with 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 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. 

For 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. Don't Allow Food Waste Down Your Drain - EVER
  3. Use A Quality Waste Digester To Control Odors and Grease Build Up - Grease builds up faster when you keep water contained, 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 big 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 get clogs because of the volume of solid waste that would back up when the liquids trickle out.



There is a large difference between your RV waste water and your household bathrooms. It may take a little extra work to keep things running in tip-top shape, but it is worth the effort to take pleasure in the little things while you travel in your RV. Start building your holding tank habits now and you'll start to make your house on wheels, a home on wheels.


Further Reading

Did you like what you just read? Check out some of our other related resources!

+ Preventing Clogs In Your Holding Tank
+ Cleaning Holding Tank Sensors
+ Eliminating Tank Odors
+ FAQ's


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