Black Tank Vent Full of Water

[bsu1980]

Hey all. When we dumped our black tank last time, we noticed a gurgling sound coming from the tank. We got up on the roof and noticed the vent is full of water. I put a 25 foot snake down the vent and it didn’t help. Any ideas as what is causing this and how to fix? Also, we dumped hot water down the vent from the roof, and the water level didn’t really change. Very strange.

Thanks all.

[Cate&Rob]

When you say “the water level didn’t really change” can you describe this further. Is the water level up to the roof vent, or well down in the vent stack?

Rob

[bsu1980]

It is up to roof level, but when I added water, the level stayed the same. It’s very strange.

[howson]

It is up to roof level, but when I added water, the level stayed the same. It’s very strange.

Very strange indeed--if the vent has disconnected from the tank below I don't understand how it would seal so perfectly that it would retain water.

Can you please fill out your signature line (as mentioned in the Welcome Letter) so we all know the year and model of your GDRV?

Thanks!

Howard

[bsu1980]

Oh yeah, will do. Sorry about that.

Dave

2021 Reflection 337RLS
2020 GMC Sierra 3500 SRW

[bsu1980]

I do wonder if the snake is going down into the gray tank vs the black tank, but I am not sure if they vent to the roof or not. It’s all very odd.

[howson]

I do wonder if the snake is going down into the gray tank vs the black tank, but I am not sure if they vent to the roof or not. It’s all very odd.

It's both. The vent "Y's" to vent both the shower gray and the black tank.



Looking at the diagram I can't come up with a theory as to how the water could back up to the roof through the vent--seems like both branches of the "Y" would have to be blocked for that to happen. Hopefully someone else can determine what's going on.

Howard

[Lonestar]

What's even more perplexing to me is that the level stays the same when water is added.

bsu1980 when you add the water to the roof vent and it's maintaining the same level, the added water has got to be going somewhere. Can you open the drain valve to each tank, one at a time, and determine if it's coming out the grey tank or black tank?

[Cate&Rob]

The only way that an over-filled tank can raise liquid to the roof vent is if that tank is the only one vented through that stack. In most Grand Design products, multiple tanks vent through the same stack. This means that (for example) if you were to leave the black tank flush running, this would fill the black tank, rise up the vent stack and then overflow into the vent stacks of one or more grey tanks. When the grey tanks fill, the overflow will come out the lowest point. Usually the shower drain or the galley sink.

Rob

[bsu1980]

I am going to call GD in the morning to just ask what they think. I really have no idea what is happening. It just doesn’t make any sense.

Thank you for the replies, I really appreciate it.

Dave

[Jlawles2]

Can you post a pic of the vent please? There are several penetration typed on the roofs of RV's now.

As for the gurgle, could it have been a back feed from the campground venting back through your hose? When possible try to re create the issue and see if you can repeat.