Good Sam Club Open Roads Forum: Class A Motorhomes: sewer odor
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Pangaea Ron

Anacortes, WA, USA

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Posted: 04/08/21 12:11pm Link  |  Quote  |  Print  |  Notify Moderator

The thru-the-roof vent was installed too low into the grey water tank on my MH and when the tank was 1/2 full the roof vent would no longer function and odors would escape through the kitchen sink drain. The tank/roof vent connection was essentially inaccessible, so I removed the air-admittance valve and tight-lined that vent to the exterior, which solved the problem.

I also raised the roof vent further above the roof line and installed a rotating Venturi cap.

Another time I found a wasp nest just under the roof vent cap. Do not pull out the nest with your bare hand while standing on a ladder. I'm glad that there was not a video.


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olfarmer

Iowa

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Posted: 04/08/21 07:06pm Link  |  Quote  |  Print  |  Notify Moderator

gbopp wrote:

Could the odor be from a faulty air admittance valve(s) under the sink?
The odor from a gray tank can be just as nasty as a black tank.


I agree, I have had trouble with those valves under the sink and the lavatory. They are cheap to replace.


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AikenRacer

Aiken, S.C.

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Posted: 04/09/21 10:07am Link  |  Quote  |  Print  |  Notify Moderator

Ours was a dry P-trap on the clothes washer.


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Bruce Brown

Northern NY

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Posted: 04/09/21 10:10am Link  |  Quote  |  Print  |  Notify Moderator

We've found sometimes it's as simple as the water in the sink traps has jostled out. Add a little more water to your sink and the problem goes away.


There are 24 hours in every day - it all depends on how you choose to use them.
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LouLawrence

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Posted: 04/09/21 04:08pm Link  |  Quote  |  Print  |  Notify Moderator

Black tanks do not require ANY additives or chemicals. Plenty of water will keep the black tank clean and odor free unless you are dry camping and trying to "hold it" for weeks at a time.

Rick Jay

Greater Springfield area, MA

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Posted: 04/09/21 05:06pm Link  |  Quote  |  Print  |  Notify Moderator

kemer,

You've gotten some great advice so far. I, too, think it's probably gray tank odor you're getting.

Funny story, though not at the time. One time when we were travelling,it was one of those days when it wasn't quite warm enough to run the A/C, so we decided that we'd open up the slider windows on the driver & passenger side and I opened one of the windows in the back bedroom. The thought being is that there would be a natural draft of nice, cool air from the front to the back. I may have popped open the roof vent a bit, as well. The kids were mid-ship at the dinette, playing some games. It sounded like a good plan.

We had been travelling and after about an hour or so, every once in a while one of the kids would say "Ewwww, what stinks?"

Well, wifey and I were up front where the nice, cool, fresh air was coming in so we didn't smell anything. We told them it was their imagination. LOL

Then when we finally stopped at a rest stop and I walked back there, I could smell the very foul smell towards the middle of the motorhome. Let's just say, it WAS NOT their imagination!

What I figured had happened is that with the air moving through the RV, there was a lower pressure created in the RV than in the gray water tank. This, coupled with the sloshing around, caused the water in the sink traps to eventually splash out enough so that the low pressure inside the RV was able to draw the gray tank odors into the rig.

Before hitting the road again, I put water down all of the drains and firmly installed the stoppers in the two kitchen sinks and the bathroom sink. That seemed to have solved the problem. I do that as a matter of course before we travel now, and we haven't had the issue since.

I wasn't sure if one of the air admittance valves might also had been faulty, so I replaced those as well when we returned home, just in case.

I like the idea of dumping Pinesol into the gray tank before your next trip. That should help you pin down which tank odors you're getting.

Good Luck!

~Rick


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Rick Jay

Greater Springfield area, MA

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Posted: 04/09/21 05:16pm Link  |  Quote  |  Print  |  Notify Moderator

LouLaurence wrote:

Plenty of water will keep the black tank clean and odor free...


Um...OK...I don't have the healthiest diet, but I would be curious to know what you and your family eats so that there is no odor in the black tank?

I mean, if the vent system is working properly, you shouldn't smell it, but it WILL be there.

I also never quite reasoned out the "plenty of water" concept, though I know many do it. I didn't want a rig with a large black tank so that I could fill it 3/4 full with fresh water. I want the capacity for "stuff"!

I NEVER add any additional water to the black tank. I mean most people pee much more than they poop, so why add pure water? The pee will do the job, basically. No problem. I DO use black tank chemicals to help break things up a bit because there may be times the rig might go several weeks between dumpings, depending upon use. I also use my black tank rinse just about every single time I dump. 99% of the time I dump I use my SewerSolution, too, which doesn't allow for that great "Whoooosh" of stuff out of the tank that a normal sewer hose allows.

Anyway, been doing it that way for about 15 years and have never had a problem with the black tank.

So...no odor, huh? [emoticon]

~Rick

IAMICHABOD

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Posted: 04/09/21 05:39pm Link  |  Quote  |  Print  |  Notify Moderator

Having the same problem with my Class C long ago,I followed all the threads on this subject,I changed the admittance valves,they were faulty,also the Pine Sol But the problem still cropped up and it was the grey tank.Until I tried what Scott G suggested...I put rubber stoppers in the bathtub,bathroom sink and the kitchen sink while traveling.

After a long and bumpy ride or thru the mountains it seemed that the p traps lost their seal.

Since then with them in place I have no odor no matter what terrain I have driven thru.

ScottG wrote:

Are you sure it's not the grey tank? As Doug indicated, it can smell horrendous. Sometimes the P-traps slosh and lose their seal. Try installing stoppers when traveling and see if the problem goes away.



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dougrainer

Carrolton, Texas

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Posted: 04/11/21 01:22pm Link  |  Quote  |  Print  |  Notify Moderator

LouLawrence wrote:

Black tanks do not require ANY additives or chemicals. Plenty of water will keep the black tank clean and odor free unless you are dry camping and trying to "hold it" for weeks at a time.


I don't know how long you have been an RV'er. But, your statement shows lack of knowledge. You just joined. So, I have 42 years as a RV Technician and I have been Master Certified for over 20 years. Black Chemical is required to help break down the Paper and solids. NOT TO MAKE THE TANK SMELL GOOD. That is a byproduct of using the chemicals.
Please respond to these questions. Doug
1. Do you leave your Black Valve OPEN when camped and the hose hooked up?
2. How often do you dump if you do not leave the valve open?

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