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Old 12-08-2018, 04:55 PM   #1
Brand: Thor Motor Coach
Model: Challenger 35MQ
State: Florida
Posts: 45
THOR #12430
Strong Black Tank Odor Inside When Backflushing

When I dump my black tank and then backflush it a few times there is a very strong black tank odor inside the RV. What could be causing this and where can I look to troubleshoot? We never experience any odors otherwise even if the black tank is half full for weeks without being dumped. I use the Valterra Flush King to backflush.

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Old 12-08-2018, 06:17 PM   #2
I Think We're Lost!
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Brand: Still Looking
Model: Tiffin Wayfarer 24 BW
State: New York
Posts: 12,870
THOR #8860
Two east places to check: the toilet and bathroom sink drains...
Dies the toilet seem to hold just a little bit of water over the valve that allows it to dump? Or does it usually seem to be dry?
If the latter is the case: there's your culprit!
The sink should have some sort of check valve in place to prevent odors from coming up from the tank. See if it is moving properly, and not stuck open.

Good luck!

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Current coach: Tiffin Wayfarer 24 BW
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Old 12-08-2018, 10:44 PM   #3
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Brand: Thor Motor Coach
Model: Axis 24.1
State: Michigan
Posts: 8,486
THOR #1150
The check valve for the sink will be in the cabinet and is called an "air admittance valve". It should only allow air into the tank and not out. Many times these aren't screwed on tight or are bad.
2014 Thor Axis 24.1
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