RV Black Tank Odor Control and Cleaning – Muck You Must Know

It is hard to think about glamping in style and great RVing when we think about the wastewater holding tanks.  RV black tank odor control and cleaning is on the ugly side of great RVing but is necessary.  When paying just a little attention to this unmentionable task will save you from dealing with the odors and sensor issues in the future.

GreatRVing Prowler
A Walk to the Campground Restroom – GreatRVing Prowler

The RV holds wastewater in tanks below the unit.  Wastewater from the shower(s) and sink(s) are held separately from the wastewater generated from the toilet(s).  The toilet waste is called black water held in what is known as the “black tank” while shower and sink wast is known as grey water held in the “grey tank(s).”

A holding tank not adequately maintained or kept clean will generate odors.  The blackwater holding tank will account for the most noxious of the smells.  Remember, the tanks under your RV are holding tanks, not septic tanks.  Holding tanks are only a vessel to store the waste until proper disposal.

RV Black Tank Odor Control and Cleaning

Controlling the Odors

When I purchased my first RV, I was concerned about the wastewater system and how it all worked.  A buddy of mine told me he only allows people to use the bathroom in his RV for liquid waste.  “No number 2s.”  A hike to the RV park’s group restrooms did not seem like great RVing to me, yet neither did a foul odor taking over the RV.  I bought the travel trailer to bring the comforts of home with me while I traveled.

During the walkthrough of my new RV, I received instruction in the use of the bathroom fan.  The fan was to be used to eliminate moisture when showering and odors when nature called.  The dealer left out one detail which became apparent regarding this fan.  As the foot flush toilet flushed, all the smells from the black tank were pulled up into the unit.  Shutting off the fan for a moment while flushing quickly became a habit for my family to control odors.

RV tank treatment tablets, liquids, and other off the shelf products will help mask the odors while the RV is in use.  These products also help break down the solid wastes and toilet paper to keep the plumbing system running smooth.  A smooth running plumbing system helps keep the tanks clean after use.

RV Toilet Usage

Most RVs and travel trailers have a foot flush style toilet.  A cassette style or composting toilet may be present in some RVs; we will discuss the proper usage of the foot flush style RV toilet here.

A foot flush toilet is operated depressing a foot lever to add water to the bowl and open the valve at the bottom of the bowl to allow the waste to drop into the holding tank.  When the foot lever is partially depressed, the valve at the bottom of the bowl does not open, but water will begin filling the bowl.  Some water is necessary for the bowl to help the solid waste flow into the holding tank.  Before use, fill the bottom of the bowl with a small amount of water.

Adding a small amount of toilet spray to the water will also help with odors.  There are several toilet sprays on the market.  Poo-Pourri is a favorite brand which is made up of essential oils which creates a barrier on the surface of the water, trapping the odor.  The toilet spray oil will also drop into the holding tank, helping to mask its smell as well.  Keep in mind; these oils are designed to sit on the surface of the water.  Toilet sprays could cause the oil to build up on the sides of the tank causing issues with the sensors.  It would be advisable to add a softening agent or detergent to the tank, so the oils do not accumulate on the sides of the tank.

RV Black Tank Best Practice

Black tank odor control and cleaning are best when the system is used properly.  To keep everything running smooth and free of odors and clogs, try keeping to these best practices:  (A short list of things I found works best for my unit)

Water Water Water
Water Water Water
  1. Water, Water, Water – Often you hear about conserving water when camping in your RV, especially when boondocking.  When it comes to the health of your black tank, water is your best friend.  Ensuring there is ample water in the tank will help the solids dissolve and keep them from drying up in the tank.  Solid waste which is allowed to dry up in the tank can become hard as a rock and stick to the bottom or sides of the tank.  Water in the tank will also help distribute any treatment tablets or solution added.
  2. Never Leave the Black Tank Valve Open – Opening the black tank valve while hooked up to the RV park sewer system will send the liquids out and keep the solids in.  Letting the black tank fill 1/2 or 3/4 full before flushing will help any solids which did not dissolve flow out of the tank.
  3. Start with Water in the Tank –  You should start with at least 1/2″ of water in the black tank.  Any treatment chemicals or tablets should be added to this water to help it distribute.  If you dump the tank during your stay, immediately add water back into your tank.  Never leave the bank tank dry while your RV is in use.  Any solids which did not flow out with the dump will turn to stone and become difficult to remove.
  4. Your Waste, Water, and RV Toilet Paper Only – With the exception of RV or septic safe toilet paper, if you did not eat it or drink it, it does not go down the toilet.  There should be no wipes, paper towels, feminine hygiene products or anything else going down your RV toilet.  These items will not dissolve and will create problems when dumping the tanks.
  5. Use the Correct Toilet Paper – Most toilet paper will eventually dissolve.  Toilet paper specifically designed for RV use will dissolve a little more quickly.  This is especially important when you will be on short trips or dumping the tank shortly after, well you know.  A good test to show if your toilet paper is right for your RV is to place a single sheet into a jar of water and then swish it around a gently.  The paper should dissolve almost immediately.
  6. Dump the Tanks and Clean – Each time the black tank is dumped, take the time to clean.  Many RVs have a black tank flush which will spray water inside the tank to help dislodge any tidbits clinging to the sides.  If your RV does not have a built-in black tank flush, there are several options for manually cleaning the tanks.  You can also add an aftermarket black tank flush if you desire.
  7. Use the Shower Sprayer to Clean the Bowl – Using hot water from the shower sprayer to clean the bowl prior to dumping the tanks will not only help get the bowl clean, but it will help dissolve some of the solid waste.  It will also add some steam to the inside of the tank to help with the tidbits clinging to the sides.
  8. Add a Little Extra Treatment when the Weather is Hot – Most treatments on the market today are capable of handling the heat but I have found when the temperature rises over about 85 degrees, the treatment is not able to keep up too well with the odor.  I usually double the amount of treatment in hot weather.

Emptying the RV Holding Tanks

Proper sequence and procedure for dumping or emptying the holding tanks will help keep the wastewater system clean.  RV black tank odor control and cleaning rely on this proper sequence.  Your RV should be hooked up to the RV parks sewer system or a dump station.  The sewer outlet of your RV is usually on the curbside of your unit to make an easy connection to the sewer connection or dump station.  A sewer hose can be attached to the outlet, usually with a four prong bayonet fitting.  There are many manufacturers of these hoses available for your RV.  RV parks and dump stations have several different types of connections.  Many of the sewer hoses will have adapters or connections which will be compatible with most of dump station connections.

RV Dump Station
RV Dump Station

Dump a full tank!  As mentioned above, when connected to a sewer system at an RV park, leave the drain valves closed until you are ready to dump.  Ideally, you will want to have a tank that is 3/4 full at the time you dump.  The idea is to have sufficient water to help flush any undissolved solids from the tank.

The dumping or emptying process is a gravity-assisted process.  Wastewater uses gravity to flow into the dump station or sewer system.  The sewer hose should have downward flow from the RV to the sewer or dump station.  Gravity will allow the waste to flow correctly.  A hose which dips or lays uphill will collect wastewater in the sewer line and prevent all the waste from flowing to its proper destination.

Dump tanks in order from the dirty to the cleanest.  You will start with the black tank, then move to the galley (kitchen) and then onto the shower tanks.  This way you will be flushing out the dirtiest water with cleaner water.

When dumping the black tank, wait for the flow to stop.  A clear fitting at the sewer outlet it helpful to watch the flow to ensure it is moving along.  Once the flow stops, close the value, add more water, and dump the tank again.  After some heavy use, I will run the black tank flush.  I add about 1/2 or 3/4 of a tank of water and dump again.  This helps flush anything left over out of the tank.  I will also make sure to give it an extra cleaning before storing RV at the conclusion of the trip.

I take extra care to clean out the black tank at the conclusion of a trip, especially when the unit will be stored in the heat if the summer.

Homemade GEO Treatment

It is easy to walk into an RV store, Walmart, or make a quick search on Amazon to find a number of  RV tank treatment products commercially available.  Black tank odor control and cleaning became easy once I found a homemade solution to keeping my tanks clean known as the GEO Method.  I am not sure where the name came from but a site I found credits a man (Charles Bruni) of Arkansas with creating this method of tank treatment.

The cleaning solution is made from several household items and works amazingly.  The solution is such common when viewed in other household applications that looking at it to clean your RV tanks just makes similar sense.

What do you need for the GEO Method?

The black tank on your RV or travel trailer is nothing more than a holding tank.  Waste is not held in the tank long enough to break down like in a septic tank.  In order to keep the muck from hanging out in there, use the GEO Method with plenty of water to flush those tanks out.

Calgon Water Softener
Calgon Water Softener

Add 2 cups of water softener to a gallon of hot water then pour the solution into your holding tanks, one down the toilet and another gallon down the drains.  Add a cup of laundry detergent to your black tank.

The water softener allows the solid waste to separate from the sides of the holding tank, and clear off those sensors.

If the odor builds up and the detergent and water softener are not keeping the odors at bay, add about a half of a gallon of liquid bleach to the holding tank.  This will kill the bacteria which is causing the odors.  You will hear some people say the bacteria is good and helping to break down the solids.  As I mentioned above, these tanks are just holding tanks and the waste is not stored for a sufficient time to break down everything fully.  Others will mention the bleach may be bad for your valve seals.  This argument does have merit.  The key is to not allow the bleach to sit in the tank for a long time.  Get the bleach in the tank, add plenty of water, allow a short time for the bleach to work, the dump the tank.  Add some clean water back in the tank and you are good to go.  No more odor.

Find the Original GEO Method Post Here

Homemade Foaming GEO Tablets

I was searching the internet looking for an easy to use solution for black tank odor control and cleaning which I can put together and just have ready when I need it.  I found the perfect solution, a combination of the GEO Method and a foaming cleaning bomb.  These do it yourself tablets are an easy solution for keeping your holding tanks clean.

These foaming tablets are made from three key ingredients.  Borax, citric acid, and baking soda.

People are already shouting “Ohh my gosh, you can’t use acid!”  Well, citric acid is fine.  It is edible, found in citrus fruits, and is used safely in all kinds of applications every day without harming people or the environment.

The Recipe:

Combine the Borax, baking soda, and citric acid in a bag and mix well.  Then add a few drops of


water to help bind mixture.  (You may notice a little bit of foaming.  This is OK just go easy on the water at this point.)  Pack the mixture into a mold and let it dry.  Once the tablets set, they are ready for use.  If they are not going to be used right away, store them in an airtight container.

Ready to clean?  Add water to your toilet.  Drop in a tablet and watch it fizz up.  It will clean the toilet.  Flush it down the tank and let it do its magic.  The foam will help clear everything off the sides of your tank.

The best results I have when I use these tablets is to dump the tanks, then add the tablet into the tank along with plenty of water.  Let the mixture slosh around a bit or foam up and do its thing.  Flush everything out and store your camper until the next trip.  If you have the luxury of having a dump station where you store your RV, take a drive home and really get the solution sloshing around for a little extra cleaning.


GreatRVing does not need to be ruined by black tank odor.  Black tank odor control and cleaning may take a little prepping and care but will be worth it.  Those black tanks will be kept clean and fresh.  No longer is “holding tanks” a dirty word.

Remember, plenty of water!!!!


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