Gray tank vent problem:A couple of weeks ago water backed up in the shower while wife was showering , when I returned an hour later I looked in shower with 3" of water in it I said no big deal tank needed dumped.Now when we fill the kitchen sink with water for dishes and drain it backs up in the shower if the dump valve is closed, but drains fine with dump valve open. Thought ok vent to tank is plugged, so I removed vent cap at roof of RV and ran water down vent pipe to clear and make sure it ran clear and it did.Clearing the vent pipe did not help and I tried stuffing a towel into shower drain so water could not come up there, filled both kitchen sinks and drained them with dump valve closed and water came up in bath sink drain. There is also a bad smell when draining sink with dump valve closed, but no smell when valve is open.My gray vent pipe does not go straight down at the top it has 2 45 fittings to move the pipe over to miss the slide-out.Any ideas to help would be appreciated.

When you open the gray tank dump valve, does a lot of water drain out? The sink water backing up in the shower makes one think the gray water drain line is plugged up 'downstream' of the shower but the sink draining OK when the gray dump valve is open makes that unlikely. When the gray tank is full, water backing up in the shower is normal but that should go away as soon as you dump the gray tank. Your symptoms are strange.

The vent pipe to my grey water tank was installed too low in the tank, and when the tank was about 60% filled, it was blocked from venting and smells came from the kitchen sink drains.When I removed the thru the roof vent cap, I noticed that the vent pipe was installed about 2-3 inches below the upper surface of the roof. I also removed the under counter air-gap? vent, and plumbed it directly to the exterior with flexible CPAP tubing. I also installed a Venturi roof vent, and do not now have issues with unwanted smells.

Could the blade valve not be operating?It is possible that the handle has come off the valve. You could open the valve and push a flexible rod up from the 3 inch hose connection to see if valve is closed. Could get wet and messy!

It sorta sounds like your vent pipe has slipped to the bottom of the tank.

Chain-drain-syndrome?One drains into the second but after the second, the pipe to the tank is blocked.

Gray tank venting problem | Good Sam Community

29 Replies

prichardson
Explorer
Dec 31, 2018
Can you see the full length of the vent pipe? If there is a portion that runs horizontal it may be pitched slightly down instead of up and is forming a trap.
enblethen
Nomad
Dec 31, 2018
Look under the galley sink for an air vent. It would be pretty high under sink attached to vent line. allows air in.
mobeewan
Explorer
Dec 31, 2018
camperdave wrote:
It sorta sounds like your vent pipe has slipped to the bottom of the tank.

Might not be all the way to the bottom of the tank but definitely sounds like the pipe has slipped deeper into the tank.

OP - the vent pipe should also be sticking above the roof. The vent pipe needs to be pulled back above the roof and new sealant allpied around it before water gets into the roof and the roof becomes water damaged. Be careful not to completely pull the pipe out of the top of the tank.
olympicman
Explorer
Dec 30, 2018
Been busy trying things so have not been able to respond to questions about my problem.

Garyemunson: The tank drains fine when drain valve pulled with lots of water flowing.

Pangaea Ron: I have this problem even when the tank is empty if the dump valve is closed. And I have checked and the vent pipe has not dropped, it is possible the installed to long of a pipe, but I don't think so.

Enblethen: The valve is opening and it dumps just fine.

Mexicowanderer: Would that cause the back up into the shower only when the dump valve is closed even with an empty tank, but work fine when dump valve is open?

Yesterday tried running a snack down vent pipe and also tried to view with an endoscope but could not tell what I was looking at.
Today I am going to run the back flush to fill tank and see if it will push water up through the shower with the dump valve closed and maybe dislodge any blockage.

Any thoughts on this plan?
MEXICOWANDERER
Explorer
Dec 28, 2018
Chain-drain-syndrome?

One drains into the second but after the second, the pipe to the tank is blocked.
camperdave
Explorer
Dec 28, 2018
It sorta sounds like your vent pipe has slipped to the bottom of the tank.
enblethen
Nomad
Dec 28, 2018
Could the blade valve not be operating?
It is possible that the handle has come off the valve. You could open the valve and push a flexible rod up from the 3 inch hose connection to see if valve is closed.
Could get wet and messy!
Pangaea_Ron
Explorer
Dec 28, 2018
The vent pipe to my grey water tank was installed too low in the tank, and when the tank was about 60% filled, it was blocked from venting and smells came from the kitchen sink drains.

When I removed the thru the roof vent cap, I noticed that the vent pipe was installed about 2-3 inches below the upper surface of the roof. I also removed the under counter air-gap? vent, and plumbed it directly to the exterior with flexible CPAP tubing. I also installed a Venturi roof vent, and do not now have issues with unwanted smells.
garyemunson
Explorer II
Dec 28, 2018
When you open the gray tank dump valve, does a lot of water drain out? The sink water backing up in the shower makes one think the gray water drain line is plugged up 'downstream' of the shower but the sink draining OK when the gray dump valve is open makes that unlikely. When the gray tank is full, water backing up in the shower is normal but that should go away as soon as you dump the gray tank. Your symptoms are strange.

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Gray tank venting problem

29 Replies

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