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Old 09-22-2024, 03:27 PM   #1
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STINK at Sink 42FSKG

My wife and I have been living full-time in our Forest River RV for over a year now, but we've continuously struggled with persistent odors—mainly the smell of rotten eggs, sewage, and gray water. It’s becoming increasingly frustrating.


I recently replaced the Dometic 320 toilet with a small residential model, which thankfully eliminated the stench from the black water tank. Additionally, it feels like I’m conserving water since I no longer have to rely on the shower to flush out the toilet every time due to its poor swirl action.
However, the shower still emits a foul odor.


Upon inspection, I noticed it lacks a traditional P-trap and instead seems to have some type of flat rubber device. I’m considering installing a proper P-trap, as the basement is both heated and cooled, so it shouldn't be an issue. In hindsight, I’m not sure why I didn’t do this earlier.


The most perplexing issue, though, is with our kitchen double sink. It has a P-trap and an air admittance valve under the sink, which I’ve already replaced with a higher-quality brand. Despite these efforts, we occasionally experience a strong odor in the RV that takes hours to clear with the vents running.


My son suggested testing by placing a plastic bag over the air valve and securing it with a rubber band, which did reduce the smell by about 60%. Yet, when we leave the RV and come back, the gray water smell is still noticeable.


I’m starting to wonder if the air valve might be installed too low. The top of the valve sits below the bottom of the sink drain, and I’m unsure if that could be contributing to the issue. It’s baffling that despite having a P-trap, the odor can still make its way into the RV.


If anyone has experienced something similar or has suggestions for a solution, I’d greatly appreciate your advice. Thanks in advance!
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Old 09-22-2024, 06:16 PM   #2
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Have you tried a deep clean of gray tank and do you use an enzyme in your tank?
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Old 09-22-2024, 06:56 PM   #3
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Quote:
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Have you tried a deep clean of gray tank and do you use an enzyme in your tank?

There is no provision for cleaning or flushing the tank at all. It's permanently tied into a single drain with the other grey tank and black tank.
Only the black tank has provision to clean.


The thing is that nothing should be stinking at all if it's properly plumbed and the equipment is not faulty like the Air valve. There is no way for the tank fumes to come into the RV unless the AV is placed wrong by being lower than the sink drain etc.



Honestly I have no clue really, I just know Forest River dropped the ball.



There is no way to flush and now I think my tanks are sagging a lot after a move. I will wind up rebuilding this thing one piece at a time 120k rv.
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Old 09-22-2024, 07:44 PM   #4
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Gray tanks can hold foul odors ..over a years worth of showers, dirty dish water, food particles, grease..it can get stinky. I’d definitely start there with a cleaning of the gray tanks. I’d also treat the gray tanks with an enzyme. Same enzyme that you may already be using in your black tank.

What IF it was that easy?? Just trying to help.
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Old 09-22-2024, 07:52 PM   #5
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We have tried all sorts of treatment.



Tonight we un-bagged the AV and it stunk like crazy. So I double bagged and stretch tapped the AV - no more stink and the drain still drains without gurgling.



I am going to buy a exterior AV box and 90 degree the thing outside the sidewall.



Now to install a pee trap in my shower. Maybe my RV will be stink free...
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Old 09-23-2024, 07:50 AM   #6
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Quote:
Originally Posted by technalyzer View Post
There is no provision for cleaning or flushing the tank at all. It's permanently tied into a single drain with the other grey tank and black tank.
Only the black tank has provision to clean.


The thing is that nothing should be stinking at all if it's properly plumbed and the equipment is not faulty like the Air valve. There is no way for the tank fumes to come into the RV unless the AV is placed wrong by being lower than the sink drain etc.



Honestly I have no clue really, I just know Forest River dropped the ball.



There is no way to flush and now I think my tanks are sagging a lot after a move. I will wind up rebuilding this thing one piece at a time 120k rv.
Look into the Valterra Flush King. It will take an adapter to connect it to the cam lock on the 42fskg if yours has the cam lock system. Also, monitor the amount of water you are sending into the take with a flow monitor so you don't overflow lol.
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Old 09-23-2024, 10:51 AM   #7
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I keep reading this thread and it just doesn't make sense. What you said is true, the p-traps and hepVO valves should prevent odors. The air admittance valve should never allow odors out when working correctly.

I have one thought not mentioned yet. You are at a seasonal site or stay at parks for longer durations? How are you connected to the park sewer? Regular flexible sewer hose? The reason I ask is that some park septic systems can have positive pressure depending on wind and vent placement. So, if you leave your tank valves open (hopefully only gray), the park system gas could potentially get into your RV. Happens to us at one particular park we enjoy.

To prevent the gas from coming up into our RV, I started always arranging our RV sewer hose to have a good size p-trap bend in it. It was either that or keep both gray tank valves closed all the time. We tend to fill gray tanks pretty quick when at a park due to tankless water heater and long showers, so the hose p-trap is better for my lazy nature

Just a thought and a SWAG.

Also possible you have a loose/broken/etc vent stack pipe or seal (where it goes into tank).
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Old 09-23-2024, 11:35 AM   #8
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Do you have a dishwasher? If so, have you used it recently? In my Class A, I had a stink I couldn't figure out and it turned out that I had not used my washer/dryer in months and the P trap was empty and allowing the smells from the gray tank into the coach.
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Old 09-23-2024, 08:59 PM   #9
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Sink smell

Had the same issue,seems after a few months,dust or whatever stops the admitted valve from sealing,every 4/6 .months I unscrew it ,soak valve in hot water and dawn, seems to happen regularly in hot weather,don't know if ac effects it but cleaning has worked for over 2 years
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Old 10-01-2024, 07:52 AM   #10
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We are in a group of campers with water and electric connections, no sewer. The water is well water and we are all using filters. This is the first time we have noticed rotten odors emitting from the drains in at least 4 different campers. One of the campers in our group used a product in their gray water drains and they do not have an odor. So I opened a pod of the granulated chemicals which I normally use for the black water tank and poured it down the gray water drain. The odor is gone. I should mention sometimes we leave the camper unoccupied for a few days. Perhaps the odors are from not using the drain for several days. We have also experienced above normal temps the last couple of weeks. I’m not sure what exactly caused the odors but using chemicals in the gray water drains seems to have solved the problem.
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Old 10-01-2024, 09:10 AM   #11
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you would be surprise what is in gray water and if you let it sit for a long time it will smell


we use to have grease traps in some of the houses I grew up in
they got cleaned out and were full of solidified fats, pieces of food , hair and everything else that got washed ...

take my word fer it, grease traps can stink like cr@p...

your gray water tank if left for long periods will be just like a grease trap and begin to grow microbes that can produce a nasty smell

Keep the tank flushed and as clean as possible
The use of a caustic/enzyme once in a while may be a huge benefit .
or flush it out once in a blue moon with hottest water you can
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Old 10-01-2024, 12:59 PM   #12
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Thanks!! The strange thing is the drains only smell when running water down them (ie kitchen sink, shower, etc.). After awhile the smell goes away until the next time when someone runs water down them. So far the product I used seems to be working but I only put it in yesterday!! I can only imagine what might be in the tanks and that is why everyone hates 'dumping'!! P U!!
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Old 10-01-2024, 01:51 PM   #13
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if you smell them when water is draining down them look for a blocked air vent
air from tank has to go somewhere when water is filling the tank

so if there is a blockage like mud dauber wasp nest up on the roof vent then the only place for the stinky air will be inside the rv.
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Old 10-03-2024, 08:34 AM   #14
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Thank you for your input Aussieguy. Perhaps if we were the only rig having this stinky problem I would agree with you. However at least 4 different rigs in our group are stinky. This stinky problem only happens at this campground so we tend to believe it is due to the well water (direct hook-up with filters) or the fact we are camping for an extended period of time like the original poster. So far using chemicals in the gray water tanks seems to alleviate the stinky smell! I will keep your advice in mind though if we have a stinky problem at another campground. Thanks again for your response.
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Old 10-16-2024, 05:48 PM   #15
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A/C is activating sink stink

have done a lot of testing -

i was using the sink - no stink and was just about done when the A/C kicked on and here come the smell.

since i would think the A/C is pulling return air from inside the RV it must be sucking air in from the sink and shooting it out the air vents?

or the A/C is sucking the air from outside where the vent stack is and shooting out inside the RV?

i replaced the AV under the sinks with a good name brand so i don't think that would have anything to do with it.

any ideas?

also we have a chopper pump permanently hooked up to a 100' 3/4" water hose and i drain the tanks one at a time when i pump them. i sometimes smell some stick when i drain the tanks outside. but it never causes any stink inside.
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Old 10-16-2024, 07:00 PM   #16
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Checked the A/C and ducting for mold and rodents? Just a thought. Had a friend with mice in the overhead ducting and ceiling. Now that was quite a stink....
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