March 26, 2023

Why Does Your RV Tank Smell?

Article - Why does my black tank stink

Tank waste buildup and poor ventilation are the primary reasons for that awful black tank smell coming out of your toilet. Cleaning your tank, upgrading to a Siphon Vent and adding odor fighting additives to your tank should fix the problem.

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How To Eliminate RV Tank Smell

Here are several tips to keep your black tank clean and odor free permanently.

  • 1. Clean and Flush Your Tanks Regularly

    Why Does Your RV Tank Smell? 1
    Flush the tank until the water runs clear

    How clean is your black tank when empty? Open the valve on your toilet and take a whiff. If it stinks, then it needs to be cleaned.

    If you flush and clean your black tank regularly, you can minimize tank waste buildup inside. Every so often, do your gray tank too. Most smells originate in your black tank, but your gray tank can also get smelly especially in warmer climates.

    Follow the steps outline in this article How to Clean Your RV Black Tank to give your tank a good cleaning.

  • 2. Install A Siphon Vent

    Why Does Your RV Tank Smell? 2
    Siphon Vent Installation – No need to replace the vent base

    A Siphon Vent replaces the standard plumbing vent cap on your roof.

    How it works – The unique shape of a Siphon Vent draws air and gasses out of your tank. It prevents tank odors from venting into your bathroom. A standard vent can create a vacuum inside your waste tank when the toilet is flushed allowing nasty air and gasses to pass through your toilet.

    Siphon vents are inexpensive. You can buy one for just a few bucks. Use this Amazon link to learn more about the Siphon Vent.

    Installing a Siphon Vent is easy. In most cases you can just pop the top off of the existing vent and replace it with a Siphon Vent. Finally, seal it up with some marine grade adhesive and sealant.

  • 3. Add Water Softener or Happy Campers Organic Tank Treatment after each Dump or Flush

    Why Does Your RV Tank Smell? 3
    Happy Camper Powder

    Of the many tank additives available, I’ve had the most success using the Geo Method and Happy Campers Organic Tank Treatment.

    The Geo Method (Water Softener and Detergent) – Mix a small amount of water softener and eco-friendly detergent (dish soap or laundry soap) with some water after each dump and pour it into your black tank.

    There are no special RV chemicals required and you can buy water softener, dish washing liquid and/or laundry detergent from any grocery store.

    Want to learn more? Here’s everything you need to know about the Geo Method.

    Happy Campers Organic Tank Treatment – Happy Campers is a very popular organic compound that helps breakdown any tank waste deposits and prevent odor. Just one scoop of this stuff mixed with water will treat a 40 gallon tank.

    Use this link to see what others have to say about Happy Campers on Amazon.

    Which method do I prefer? I use a combination of the two. I mix a scoop of Happy Campers and two lid-fulls of Calgon Water Softener with five gallons of water after each dump.

  • 4. Don’t Leave Your Black Tank Empty

    After dumping, put a few gallons of water back into your black tank. Without enough water in the tank to move things around, poop and toilet paper will pile up…literally. We call it the “Poop Pyramid”. Get the picture?

    How much water should you add back in? I like to add enough water to cover the bottom of the tank. How much depends on the shape and size of your tank. Four to five gallons usually does the trick for my black tank.

  • 5. Dump Only When The Black Tank Is Full

    A full blank tank generates lots of pressure when the dump valve is opened. This is what you want. The pressure generated when dumping a full tank helps force the contents out of the tank.

    Once you release the tank valve, let it flow until it is empty.

    You may be tempted to dump your tank when it is only a half or quarter full. Avoid doing this. You’ll leave more waste behind if you do. Why? A partially full tank does not have as much pressure as a full tank.

  • 6. Keep Tank Valves Closed When on Full-Hookups

    Open the valve only when it is time to dump then close the valve immediately. You don’t want odor and stank from the RV park’s sewer system to come through your sewer hose and into your RV.

    Another option is to create a “P” trap in your sewer hose. This creates a dip in your sewer hose that’s shaped like a sideways letter P. The low spot of the dip creates a barrier between your RV’s sewer system and the park sewer.


I hope these tips were useful. Follow them and those sewer smells inside your RV will become a thing of the past. Do you have a friend with a smelly tank? If so, share this article with them.