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Old 10-14-2010, 07:17 PM   #1
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2003 Ultimate Advantage Stinky!

We can't seem to find the source of this horrible sewer gas smell! We've replaced under-the-sink vent flapper caps. Still stinks. Doesn't happen all the time. Always happens when we take off driving...eventually goes away. Help!
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Old 10-14-2010, 07:44 PM   #2
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Check your toilet. If it won't hold water in the bowl the seal may be bad or needs to be cleaned. Toilet paper can easily get stuck in the seal when flushing and allowing the valve to slam shut to soon There needs to be a small amount of water in the bowl to prevent gases from flowing thru the coach especially when traveling.

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Old 10-15-2010, 07:51 AM   #3
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We have the same problem with ours.. Have had a lot of monday quarter backs try to tell us what the problem was.. I put a plastic bag over the vents That are up under the sinks Both The Bath and Kitchen, IT still smalled.. Now It would only smell when the Black holding tank was over 1/2 full. We would stop dump , And no more smell. My personal Thoughts. Any designer that has the Sewer vent come backinto the coach, Needs to go back to his previous Job ,, A sign holder at A construction site;; Vent a sewer into the coach. Think about that; Sewer gas Is extreamly Explosive, plus it does not smell so nice;; Just the facts;; I know this will upset many people. maybe it will get some to use there head also.. Life is good .. when the holding tanks don't smell;;
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Old 10-15-2010, 09:27 AM   #4
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Our toilet seems to be ok. We are greatful for your input.
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Old 10-15-2010, 09:32 AM   #5
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Only time we get black odor is when we travel with either of the two rear-most ceiling vents open. I would suspect a bad seal on an inlet pipe to the black tank, most likely the commode inlet. Another possibility would be the vent stack inside the wall ...different floor plans have it in different locations. My gray and black tanks "Y" into the same roof top vent ...a joint could be loose, etc. But I would think a leaking vent stack would stink regardless of the fill level of the tank. A bad seal on an inlet pipe would leak when the contents get high enough to slosh against it.

The siphon breakers under the sinks are not "vents" though in some fairly rare situations they can leak some "stink". The are not at all unique to Winnebago or any single mfg'er. They often get blamed when the problem is elsewhere. It should be obvious that if they have been capped, bagged, etc and you still have stink, the siphon breakers are not the problem!
Paul (KE5LXU) ...was fulltimin', now parttimin'
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Old 10-15-2010, 09:49 AM   #6
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I am going to check the toilet seal today. Thanks for sharing your knowledge.
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Old 10-15-2010, 10:20 AM   #7
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You never travel with any windows or vents open. In a motorhome that is a NO NO,, as one never knows were a exhust fume may be sucked in , And thats not good. The heater/dash air is the only air intake.....
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Old 10-15-2010, 09:26 PM   #8
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We had a situation like you described. I found the problem to be a 3" diameter x about 3" long connector that is between the black tank and the dump valves assembly. It was starting to dry rot and would not seem to leak while just sitting. When moving the coach the tank contents would apparently slosh and cause more pressure against the connector and it would seep. It was pretty easy to replace but not so easy to access. On our model (40J) the compartment wall just forward of the wet bay had to be removed (just a bunch of screws). After the wall section is out there is a "wall" of 1" styrofoam that has to be broken away. With the styrofoam removed you can see the valves and the connector. It's just limited working space be doable. Make sure the tank is empty and sanitized with some Clorox before you open it up. Hope this helps you out.
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