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Gray Water Tank Odor Solved

15 posts in this topic

We noticed a gray water tank smell on occasion in our Gulf Stream Tourmaster. We typically noticed the smell when the coach was closed up and the ceiling power vents were running. We also noticed it when we were driving down the road. The smell originated in the rear of the coach by a small sink and the washer/dryer combination. The only place the gray water system could vent back into our coach is where the clothes washer discharge hose empties into the gray water system plumbing. We placed some foam around this connection and the smell was gone. Problem solved. Hope this helps.

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Is there a P trap on that line? If so, is there water in it?

Brett

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That's a common issue. There probably is a P trap on that drain line but it's small and the top of the stand pipe is open to atmosphere so if the water that forms the seal in the trap isn't there, you will get that odor. If the coach stands for a while without running the washer-drier it can evaporate. Many times the water can get sucked out of the trap when dumping the gray tank. That depends on the vent for the gray tank. If the gray tank vent can't keep up with the masive outflow of water when draining the tank a vacuum will form in the tank and it will suck the water out of the trap. It all depends on your vent design and how much water you are dumping at one time. What we do to correct it is to run the washer on a fill cycle for about 15-30 seconds, then cancel the cycle, begin a spin cycle to drain the water, and then cancel it after another 30 seconds. That will refill the trap with fresh water. Ideally, a closed system that used a vacuum break valve would be a better design than an open stand pipe.

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On both our 2005 and 2009 Mandalays, we had sewer odors when we first headed out. We added a Cyclone Sewer Vent, available at Camping World for $20, and have had no odors since.

Susan

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After having Campingworld install our washer/dryer we began experiencing gray water odor while driving. We inspected the installation and found they had not installed a trap in the vent and they gave us a difficult time about it. We insisted they install a trap, but in Arizona, it doesn't take long for evaporation. So before a trip, we run the washer for a few seconds and then cancel the cycle to drain the machine. We also installed a cone thingy for the top of the main gray vent.

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As a follow-up: Our coach also has stackless vents that utilize a diaphram. While not positive I believe that they allow air into the plumbing system to prevent a vacuum from forming but, prevent grey water from escaping. Happy Trails To All!

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I'm curious as to whether a trap is required for washing machines? I Just had Camping World install a washing machine and they did not plumb a trap. That surprised me. I would think that would be standard practice and important to prevent unhealthy conditions. What does the industry require? What would Camping World's reasoning be?

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Skinny,

Welcome to the Forum. The answer is cost.

For those that have the hook ups but no washer/dryer you can pour Pink RV Antifreeze in the trap. It will not evaporate like water does.

Herman

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I'm curious as to whether a trap is required for washing machines? I Just had Camping World install a washing machine and they did not plumb a trap. That surprised me. I would think that would be standard practice and important to prevent unhealthy conditions. What does the industry require? What would Camping World's reasoning be?

CW is becoming well known for their incompetence and frequent failure to use common sense when working on rv's. I would take it right back to them and have the service manager explain why it wasn't done, then insist that it be done. :wacko:

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We had this problem on a 2003 Pace Arrow I purchased used, it took a while to figure iit out. Building codes require one I don't see any difference. Does RIVA require one?

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I have a 2008 Holiday Rambler Ambassador 40SKQ. We just returned from a five day camping trip. On the second day I noticed a foul smell coming from the closet in the bathroom, especially in the upper portion of the closet. There is an option for a washer dryer to be put in this closet. There is a false wall hiding the water and waste connections for this option. Days three four and five the smell got much worse. I did dump the grey tank and drove 150 miles home. The smell was still there but much fainter. Any suggestions on a fix?

Jack Landon

F435890

Oro Valley, AZ

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Jack, Do you know if the waste water drain for the washer has any kind of cap on it? If not, that is probably where the smell is coming from. There should be a trap on that drain and it should have water in it. If you can remove false wall and pour a cup or two of water into the drain to fill the trap, the smell will probably go away. You can add a little oil on top of the water to keep it from evaporating so quickly. I think you can also buy a PVC cap to put over the end of the waster water drain where it comes out of the wall. I wouldn't glue the cap on though just in case you decide to get a W/D in the future. You can tape it with duct tape or similar.

Let us know if this works for you.

Jack

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Jack,

I will try to locate the area where the W/D drain would be in the unit. I think your assessment is right on!

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The drain will be at the back of the closet directly behind where the washer would sit. It will be a drain pipe, probably plastic, that the washer drain hose will go in. It is virtually identical to what you would find behind the washing machine in your stick built home. Just pour a couple of cups of water into the pipe. If you add a little oil after the water, it will help keep the water from evaporating. You may have to remove the back wall or a panel in the wall to see the drain pipe. On some motorhomes, I have seen access to the drain and supply lines on the side of the cabinet. You might look of either for a door or removable panel on either side.

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I located the access panel in the closet for the washer/dryer connections. I found a cap plug loosely installed which probably caused the odor. I added several cups of pink antifreeze and then installed a rubber expansion plug in the drain. The weather has been much cooler but I have not noticed any odor from the closet.

Thanks to all who added to my original post. Happy Thanksgiving to all!!

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