Dave Solberg

Diagnosing Wastewater Odor in Your RV

Dave Solberg
Sign in
Duration:   1:18   mins

If you notice a strange odor in your motor-home, it’s important to know what to do to diagnose the smell and attribute it to a specific part of the vehicle. In this RV tips demonstration, Dave Solberg teaches you how to determine whether an odor is due to an issue with the propane, grey water or black water tanks.

Dave uses some simple RV tips to solve the problem. Step one to diagnosis wastewater odor in your RV is deciding whether it might be caused by a propane leak. Propane has a very distinct, powerful smell but faint amounts can be confused with a black water or sewage tank odor. Either way, if you smell the distinctive “rotten egg” smell and are not sure, play it safe, get out of the rig and shut off the propane at the tank. Let the unit sit for a while and if the odor is gone, you should take the unit into a certified RV propane specialist to have the system inspected.

Most of the time with RV tips and techniques for maintenance it’s a game of one or the other. If you decide that the smell is not propane, you can narrow it down to either the black water or grey water tank. Even with the RV tank treatment and deodorizer products available, black water tends to have a much more potent odor than grey since it is mostly sewage. Grey water is typically shower and faucet drainage, however dumping cooking waste such as grease, milk, or other spoiled liquids down the drain can cause some rotten smells as well. Even fairly clean shower water left in a grey water tank for an extended period of time will develop a rotten smell of it’s own.

Both grey and black water tanks require a venting system that is plumbed up to the roof of the RV. This eliminates a vacuum and provides proper drainage. An annual inspection of the roof vent or vents is a an essential part of RV tips and should be done any time you experience this type of odor inside your RV. During inspection, check to make sure the vent cover is in tack, nothing is clogging the opening, and there is no gap around the vent pipe allowing air to circulate back down inside the coach.

Make a comment
  • (will not be published)

8 Responses to “Diagnosing Wastewater Odor in Your RV”

  1. LEO

    I have a 2017 Thor Hurricane 29M and when driving if there is any waste in the black tank, I get smells in the coach. Lately, it was so bad our eyes were burning from amonia odors. It was worse than a Honey Bucket after a week of use in the hot Texas sun.
    I gave tried different overhead vent combinations open and closed. I keep water over the flush ball valve. I keep the bathroom door closed to keep the smell out of the coach, but open the door, and its a gagging event. It us getting old.

    • Customer Service

      Hi Leo!

      If the vents are all closed and there is water in the bowl there shouldn’t be any odors coming in. The only other things that could let odors come in would be a toilet flange seal that is bad or a vent pipe in the wall is cracked. It is possible the black tank itself is cracked as well. The toilet flange goes directly into the tank and the only opening in the tank besides the drain is the vent that comes out of the roof. If you have vents open it can allow smells to come through but if the vents are all closed and there is water in the bowl nothing should be coming through. I would first remove the toilet and replace the flange seal. When doing this, inspect the flange and piping for any cracks and make sure the tank hasn’t dropped down. If you see any cracks or the tank has broken away this could be the source of smells. Also make sure the top vent stack isn’t blocked, this can allow fumes to travel back down into the walls. You could always take the vent cap off and make sure the pipe coming up is sealed from the side walls. I have seen this pipe cut too short which would allow smells to travel down as well. The best place to start is the flange at the floor for replacement and inspection.

      Sincerely, Dan RV Repair Club Technical Expert

  2. Sylvia Rutherford

    Ticket#20166 Both kitchen sinks have stopped draining. Noticed an “off” odor yesterday before clog occurred RV new to us and not sure where to start. Added baking soda to drains, let it sit for a while, then added white vinegar. Can still see water in drain, and its still “working”.

    • Customer Service

      Dear Sylvia,

      Thank you for your patience. In regards to your question-

      Both drains in the sink will be going to the same trap, there could be a blockage or bad venting causing the water to not drain. Have you tried draining the tanks? The kitchen sink a lot of times has it’s own tank known as the “galley” tank. It is another gray tank. If you have a monitoring panel that shows how full or empty the tanks are, check and make sure they say empty. Make sure you are pulling the valves to all gray tanks outside. The black tank is connected to the 3″ plumbing which only goes to the toilet, the smaller plumbing goes to the sinks and showers. If you are sure everything is drained, you want to remove the vent valve by the sink. It will be located under the sink. Follow the trap to where it goes down into the floor. There should be a stack standing straight up with a black top. This is the vent, it has a check valve inside to allow air to escape when the water goes into the tank. You can twist this vent off, if the water now drains then the vent is bad and needs replaced. If this doesn’t help, there could be a blockage in the plumbing. Most likely the trap. You can put a bucket underneath and remove the trap and inspect or you can try to “snake” the drain. I hope this helps!

      Dan RV Repair Club Technical Expert

    • Customer Service

      Hi John,

      Your toilet would not have a vent as it’s not a closed system like the other plumbing pipes. The vent is only designed to allow air in as to not create a vacuum, not really vent out smells. When you push the toilet pedal down to flush, the valve opens and this allows the fluids and such to flush down with water into the black water tank.


      RV Repair Club Video Membership

      We’d love to have you be a part of our community. We are convinced you will enjoy the benefits of becoming a member and having access to the best instructional how to videos and professional tips. We would like to offer you a special promotion for your first year membership.

  3. Stevanna

    When I flush the toilet there is a rotten cabbage smell. I have cleaned the tank as thoroughly as I can with a wand and a spray into the tank. I use tank deodorizers. The tank is a 50 gallon tank on a Class A.

    • Customer Service

      Hello Stevanna,

      First I would suggest checking your roof vent to make sure you are getting the proper ventilation which should not allow the smell to come into the coach through the toilet? Maybe change the old style vent with a new Cyclone (see the video on the site) which changes direction with the wind like a windmill and the air/wind helps pull out the smell? Next, dump about 30 pounds of ice down the toilet, 1/4 gallon of bleach, and 20 gallons of water and drive around for about 30 minutes, let it set for another couple of hours for the bleach to work in, and then drive around for another 30 minutes or more. Then dump the tank, fill it 2/3 full of water again, and dump it, run the wand down the toilet for a good 10 minutes, fill the tank to 2/3 and dump again.

      One last tip, make sure the bathroom vent fan is not running when you flush the toilet! The fan will pull odors from the tank into the bathroom.

      David RVRC Video Membership

Get exclusive premium content! Sign up for a membership now!