Last week my drains started gurgling and draining slowly so I climbed up onto the roof to check the vent and possibly snake it but found that it is full of water up to about 6' below the roof line. I wanted to do a little more research to make sure I am taking the correct actions but am not finding much on the topic. I know that the gurgling indicates venting problems (which it is clearly not venting if it's full of water, lol) but I was wondering if a main drain clog or a full septic tank can cause water to back up the vent? Where did all the water in the vent come from? It's only been acting up for a week and we have had very little rain in that time (and the vent does extend 18" above the roof), I'm afraid to open the cleanout and end up with 20+ gallons of "water" in my basement unless it is actually going to correct the problem.

So, what is the best/most effective plan of action to correct this?

I would run a cable down the vent. I'd bet that it's not full all the way down, probably only a small section.

A partition blockage between the house plumbing and the septic tank, may be the issue, that is causing the water level to rise in the sewer vent. Granted your septic tank might be full and back flowing, but you won't know until you open the cover and see.

Good Luck in the cold weather n snow
Best Wishes

I snaked the vent about 30' down and the water went down rather quickly but then I came inside to check for improvement and I still have gurgling drains/toilets.

I dug up the cap for the septic but am unsure how to determine if it needs to be pumped.

If the entire pipe were full, your house would have been flooded a long time ago, as it would have been before water could possibly rise that high in the pipe, (the water would have to be as high INSIDE the house as it was in the pipe.

quote; that is causing the water level to rise in the sewer vent.

Up to the roof level, without flooding the house? I do not think so.

Removing a cover "under pressure" is a job for professional. Your septic service provider should be advised.

Best Wishes

Today they pumped the septic (about an hour ago) and the gurgling has stopped but still draining slowly. It does appear that part of the problem was a total blockage in the vent that has now been cleared and when they pumped they did have to agitate the tank 3 times to break it up enough to pump. So clearly, the tank was in need of being pumped too. Does it take some time for things in the house to start moving better after having been so full?

In our (tiny) town, we pay a monthly city bill that covers pumping and trash services but the city owns the pump truck and they require us to dig up and remove the cap prior to them coming to the site.

The plumber came today and fixed it!! The septic was so full before pumping that the horizontal drain had built up sediment in it. He also advised pumping every 2 years with the size of our family. Thank you for all the guidance, it is good to know that everything is corrected and how to prevent it from happening again.