Can a clogged black tank air vent cause toilet clogging?

[Lee]

Does the air vent that goes out of the roof have anything to do with waste not going down into the tank?
This has happened frequently (I haven't checked the vent yet), but I'm a full time RVer I always get my tanks emptied every 2 months. Yet for the last 4 or 5 months one month after getting it emptied (a company does it) the toilet bowl will fill up with liquid and nothing will go down.
I treat the tank with plenty of enzymes that are supposed to unclog any pyramids or solid waste.
This time I've put more water down the toilet than I have in the past hoping it would do the trick.
I never put tp in the toilet.
I've tried a snake auger
I tried a small sink plunger today, no luck. I'm going to get a bigger plunger today.

Will a plugged air vent cause the issue due to inadequate air flow?
Thanks in advance 🚽🙏🏻

My trailer is a 2020 crossroads zinger 290 kb

[DavisK]

Does your camper have a black tank flush? If so, does the company that empties the tank flush it after emptying it? What size tanks do you have that are large enough that you only need to dump every 2 months?

[Lee]

Hi, I don't think it has a black tank flush but I rinse it out as it's being pumped out.
It's 39 gallon tank.

[dagst1]

I would think you have other problems. The toilet sits over the tank and other than the floor thickness it is a straight shot. Not getting into your personal habits and not knowing your family size but emptying the tank every 2 months seems like a long time. Could it be the tank is just full?

[mark5w]

It's possible that you do have a poop pyramid. Me personally would dump the tank every two weeks at the most. Two months is way to long for it to sit. It may harden. Does your gate valve open for the tank, assuming you are connected to a sewer dump.

[Lee]

I also thought/think it's a pyramid but it keeps happening despite doing everything I can to prevent this. No I'm not connected to a dump. I'm a full timer and have a company empty it when it's full.

I guess emptying it more frequently would remedy this, along with using even more water than I already have been.

[dagst1]

I have heard of this so it maybe something to check on yours. The pipe from the toilet into the tank was too long and just a couple inches off the bottom of the tank so it did not take much solids to start a clog or pyramid. Not saying that is your problem but something to check.

[Lee]

Ok thanks for your input ��

[jmnsn57]

I believe the answer to your question is Yes/Maybe. All plumbing relies on air displacing liquids through an atmospheric vent. Think about your home. There is a vent to the roof, if air doesn't enter that vent, the sewer line wont flow out to the appropriate sewer. If you don't have air admittance valves on horizontal lines to the stand drain, they may not evacuate. Look at dishwasher plumbing drain connections - same is true. Many suggest an air gap install.

[Lee]

That's exactly what I've been thinking! Thanks for pinpointing what my suspicions are. It could very well be other things causing this problem but I'm going to get on the roof tomorrow and see what I figure out. If I figure anything out I'll report back here

[dagst1]

I would think if the stack was blocked it would not dump very well. Like pouring water from a milk jug it will burp air back into it but cut a hole in the bottom-your vent pipe- and the water runs out fast with no burping. When you flush it is not enough to block the discharge pipe that it would create pressure in the tank. Also when the company pumps your tank if the vent was clogged it would be difficult to do so. As the liquid goes out air must come in so if the stack was blocked it could create a vacuum and implode the tank.

Next time it is empty turn off the water and take a look down the discharge pipe. There may indeed be a pyramid.

Again just my thoughts on the subject. What ever the solution is please let us know.

[660catman]

Does the company who empties the tank have a clear connector to see if anything is coming out? For the life of me I can’t understand how you can go two months without emptying the tank.

[Lee]

Hi yes they do and we can see the water becoming clear after all the grossness. If everyone must know it's a big tank and I don't poop a lot, you're welcome. I live in it so I don't think there's any way it could be drying out.

[Lee]

Yeah every time I've looked down I see no pyramid or anything of the sort. Tank contents always come out of the tank when it's being emptied but the toilet itself will fill with liquid and no matter what I do won't go down. In fact it seems to be rising a little each day. I'm stationary and don't own a truck otherwise I'd go empty and clean the tank. Perhaps it's time to buy a portable tank in case of an emergency...

[Lee]

Here's a photo of the vent on the roof, now I will figure out the right way to open it and do more investigating...

[Lloyd]

There is more than likely a screw holding that cap onto the PVC pipe underneath it.
Try looking under the over lapping part of that cap. If you don't see anything there, take that gob of black stuff off that's on the cap. They usually have a screw holding them on. Once that's out it's just a simple matter of pulling it off.

[Lee]

Ok thanks!

[Lloyd]

Once you get the cap off, stick a garden hose in the top and turn on the water. If the pipe/stack is plugged, it will come out the top of the pipe/stack. If the pipe/stack is not plugged it should run into the tank.

[Papa-T]

Originally Posted by Lloyd

Once you get the cap off, stick a garden hose in the top and turn on the water. If the pipe/stack is plugged, it will come out the top of the pipe/stack. If the pipe/stack is not plugged it should run into the tank.

Good advice! Let us know the outcome.