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I have a 2007 class A that we bought in Feb of this year.  when we have full hook ups all is well, when we dry camp and use the toilet all is well until we start to move. then it is like a porta john is open in the living area.  once we dump, it gets better very slowly, like over a week or so.  WHAT IS GOING ON?  ive never had this issue with any RV that i have had.  I installed a tank sprayer, that seems to help but is there not a vent or something?  i put water in the toilet bowl to make a seal, no real noticeable difference.  i filled the tank and put in the black packets and left them for 2 days then dumped again.  it helped at first, but it returns everytime we travel with anything in the black tank.  any advice ?



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If you haven't found this out yet , the grey tank stinks just as bad as the black . 

Start plugging all of your drains ( sinks and shower ) before travel and you'll likely find the cure for your bad small problem . ;) 


Edited by Pat & Pete
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5 minutes ago, Pat & Pete said:

Start plugging all of your drains ( sinks and shower ) before travel

We started doing that, even though we sit for a month at a time, usually.  I have a flat sorta rubber potholder we put over the shower drain, and a little tiny plug for the bathroom sink.  Also helps minimize those teeny-tiny flies/gnats that seem to spawn in the tanks.  As soon as most of the water in the shower has drained, maybe... couple hours after a shower, we put that on.  And the one in the sink stays unless we're using the sink, simply because it drains faster/better.

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You also very likely need to replace the plumbing vents that are located under each of our sinks. They are there to allow the sink to drain freely and yet to prevent sewer oders from backflowing into the RV and if they are bad you will get significant odors. You can get replacements for a few dollars from Lowe's, Home Depot, or most any home supply store.


Edited by Kirk W
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Have a look at your roof vents. Venturi affects as you drive is meant to draw out not in. Your roof vents may be blocked or not working. Also do you travel with any roof vents or windows open? The stink may come out your roof vent just to be sucked back in through an open vent. Close everything and pop a dash vent open to give your rig positive pressure as you travel.

FWIW we have friends would had a half million dollar motorhome. It smelt terrible inside. They simply could not find the cause. So in the end it got so bad they sold their rig.


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im going to check the vents.  I usually drain the grey via a water hose into a field or wherever i am.  so i dont think it would be the grey.  also, if you flush the toilet, its like a gas bomb hits you in the face and thats the same smell. so i am fairly certain it is the black.  but i am going to try all.  i think i will install tank sprayer in grey as well. 


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Empty tanks smell just as bad as a full or partially filled tank .

And , I've replaced all the air admittance valves ( drain vents ) and still had odors while on the road , until we started closing all drains . I even went up side and made sure the tank vents were open by dripping a heavy nut on a string down each . I almost always have my drivers side window wide open . ;) 

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If you are getting a blow back of air from the tank each time that you flush then you do have a vent problem. It may be that the pipe for the vent line up to the roof as slipped down into the tank and is blocked as that would be the most common cause of the black tank vent being blocked. When you get up on the roof, remove the cover from the black tank vent so that you can see the pipe as it should extend up an inch or so above the roofline. If it is below the roof the farther it is down the sooner the tank  contents will block that line. 


You may have a vent cap that only the top needs to be removed or you could have on that you must take the entire cap off to see what you have. This shows it with the cap completely removed.  The nest is the easier one to check. 


And this shows what your plumbing propbably looks like.


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