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Old 02-08-2015, 01:55 PM   #1
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Sewer odors

we had a class C rv for years and never had problems with sewer odors - until we bought our 2002 Winnebago adventurer. We had lots of odors under the bathroom sink and so replaced the air vent valve under there. the odors continued so the Winnebago dealer taped the air vent shut. This didn't seem right, but they are the dealer. We then discovered the odors were from the rv park. Fast forward a couple of months - we left the tape around the vent in place and odors came and went as we went from one park to the next. Some were worse than others. Then about six weeks ago, we woke up to a horrible odor in the bathroom coming from the toilet. We dumped the black water even tho it wasn't full and deodorized. The odor went away and all was good for a couple of weeks and then suddenly again first thing in the morning, we had the horrible odor and once again dumped, etc. We used to go about a week without dumping the black water and never had bad odors, but now sometimes after a couple of days - it is really bad.

There is no warning such as an increase in odor - it is just kaboom - horrible!!

We are wondering if it has anything to do with the taped air vent even tho that was for the gray water or we also had put a plastic bag around this strange "U-turn" hose that is under the bathroom sink. We were told this "U-turn" hose is a pressure reducer for the sani-flush for the black water tank.

We also get bad odors when our gray water tank registers full. Another oddity that has recently happened is our gray water tank never registers below 2/3 full and seems to fill up quickly.

Does it sound like something is broken or we just don't know how to do this?

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Old 02-08-2015, 02:48 PM   #2
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Hello, the frustration on this can drive you nuts, because there can be many things causing this. Heres a link to all the past posts at IRV2, hope it helps. A lot of reading!

Dances with wolves
Linda and Bob.
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Old 02-08-2015, 03:05 PM   #3
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The previous owner may not have kept the black tank as clean as he should have, resulting in the famous "pyramid of doom"!

I would order the Happy Camper Extreme treatment and follow the instructions carefully. Then after the tank is clean, use the regular Happy Camper treatment every time you dump the black tank.

You need one of the clear 45-degree sewer elbows between the hose and the tank so you can see when you have it clean.

If your coach does not have the built-in black tank flusher, I strongly recommend you have one installed.

Good luck, happy trails, and God bless!
Joe & Annette

2002 Monaco Windsor 40PBT, 2013 Honda CRV AWD
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Old 02-08-2015, 03:29 PM   #4
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Remove the tape from the vent. The system needs to be vented as it can build-up pressure. Flushing the toilet will allow the gases to enter the MH. (with a taped vent)
2016 Thor Tuscany 34ST XTE, Freightliner XCR, ISB 360hp/800tq. Allison 3000, Koni FSD shocks, Roadmaster 1.75" front sway bar, Safe-T-Plus, DYI air bag flow control valves.
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Old 02-08-2015, 06:13 PM   #5
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I also put deordorizer in the gray water as we would sometimes get a smell from the kitchen sink.
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Old 02-08-2015, 06:58 PM   #6
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I had a very similar problem, found the vent on the roof clogged
(mud daubers) The seal at the base middle and base of the toilet both needed changing, and finally the vent line from the vent line to the roof had come disconnected. Had to remove the passenger side panel to repair it, a little pvc glue and problem solved.
This bus has been an extreme learning curve this forum has helped a great deal, thanks to all that have provided advice.
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Old 02-08-2015, 09:39 PM   #7
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We had an oder issue also.

With our new to us pusher we took off to Colorado last year. Wasn't long before we could smell that smell in the coach. After searching I figured out the route the oders were coming from. The black water tank dump valve had started to drip ever so slightly. The shower stall is almost over the plumbing station compartment. There is a vent that airs out under the shower stall thats not sealed off to the basement. So... as were driving down the road a vacume is formed in the cabin and the oder was sucked into the living quarters. Short term solution was to dump the tank every day and I also removed the shower vent grill and closed it off with masking tape. When we got home I replaced the valve seal and the problem went away. Sounds like you might have a leak or some plumbing that has a broken seal in the basement. You might want to see if the "P" traps in the sinks are holding water, if they aren't the oder could be coming up the drain pipes.
Good luck, Mike
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Old 02-10-2015, 10:05 AM   #8
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These are good suggestions; thank you. Reading my original post, I was obviously frustrated and perhaps didn't do a good job of describing the issues - bad smell under bathroom sink when vent is not taped and horrible toilet odor every once in a while. The toilet odor goes away when we dump. Seems simple, just dump the tanks. But, sometimes it happens after just 2-3 days and is not a gradual increase in odor, but a sudden horrible stench usually about 5 am - terrible way to start the day.

I would think if we had the "pyramid of doom" that the toilet would smell terrible all the time??

I removed the tape from the vent under the bathroom sink and within a few hours, the bad smell came back under the sink. I wish I knew if this vent is connected to the black water system. It doesn't seem to affect the toilet odor we had as our bathroom now smells fresh and clean, but under the sink is bad.

We deodorize the gray tank every once in a while and the black tank at every dump. We have a built in flush for the black tank and use it.

If our sporadic odor came from a bad vent on the roof - would it smell bad all the time?

Are the "p" traps in the sinks connected to the black water system?

I would think the black is totally separate from the gray - "p" traps, vents, etc. ??

Altho we have RVd for 20 years, we've never run into so many odor problems. We've also had very bad luck with rv repairmen and obviously we aren't very good at solving our own problems. I would gladly pay someone to fix the odor issues if there was a guarantee that they could be fixed. We just can't keep paying someone to "not" fix stuff.

Again, thank you.
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Old 02-10-2015, 10:25 AM   #9
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Check your open and shut grey and black valve configuration. Our valving allows the two systems to be tied together which can sent stinker Black waste to the gray system.

Also check your under the sink anti-suction vent, it could be faulty.
2016 Thor Tuscany 34ST XTE, Freightliner XCR, ISB 360hp/800tq. Allison 3000, Koni FSD shocks, Roadmaster 1.75" front sway bar, Safe-T-Plus, DYI air bag flow control valves.
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Old 02-10-2015, 10:25 AM   #10
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I add plain pine sol to both my tanks occasionally really makes everything smell fresh. Best to drive a few miles to let it work its magic. We always treat our black water tank with Campa-Chem original and have never had any bad odors. 🚐😀 Good luck.
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Old 02-10-2015, 10:39 AM   #11
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The bathroom sink is usually tied into the blackwater tank instead of the grey water. The kitchen sink and shower are connected to the grey.

We just purchased a 2002 Holiday Rambler coach. We get a bit of odor in the bathroom when the tank gets toward full. I m thinking of changing the toilet gasket and see if that helps. Have you had that done?

Also, right after you dump the black tank, shut off the water to the toilet and look down into it with a flashlight and see if it's getting cleaned out properly.
Brad and Pat, the Dad and Mom-Dawgs with Kiddo and Dinah-Mite, the Dawter-Dawgs full timin' in our 2002 HR Neptune DP with 2015 Indian Scout Toad
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Old 02-10-2015, 11:05 AM   #12
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It sounds like you've tried everything....here are some more ideas.

A recent poster searched and searched for odors just like you for a long time. He finally checked the tanks and saw that he had a broken black tank pipe where it entered the black tank. It was leaking.

Check behind your toilet, often there are some small openings and even big ones where the plumbing comes through the floor. Make sure those are sealed, as they can let tank odors migrate up from the tanks and valves.

Last thought.....do you have a SaniCon macerator on your coach. If so, the OEM 3" hose provided by SaniCon is semi permeable and will allow sewer odors to escape. It needs to be changed out to a better quality hose.
Don & Mary
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Old 02-11-2015, 04:24 AM   #13
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Don't know where you live, but if near Red Bay, Al. Try Custom RV, Brandon is good, he used to work for Tiffin but has opened his own business. His reviews are all very good.
Ed & Kathleen
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Old 02-12-2015, 08:01 AM   #14
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The bathroom sink is usually tied into the blackwater tank instead of the grey water.
I wouldn't say "usually", but it's a definite possibility.

It should not be necessary to tape up the air admittance valve under the sink because a properly operating valve will be closed all the time anyway. If replacing the air valve didn't stop the odors, maybe the pipe itself is cracked or somehow interfering with the valve "flapper". But it's not a big deal to tape it up either - the system is vented via the roof vent. The primary purpose of the Admittance Valve to reduce suction that can pull waste water out of the drain trap (that U-shaped pipe in the sink drain), e.g. while dumping the tanks.

I would be concerned that the toilet is not properly sealed to the floor flange, or that the pipe through the floor is not fitted tight at the tank. Also make sure that the roof vent is open - you can run a drain snake down it or squirt or a water hose through it (the water goes into the tank, so do it when you have room or are hooked to sewer).

Gary Brinck
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