We had the sewer drain water back up into (and over) our downstairs bathroom toilet, and of course ruined a section of carpet installed just late last year.  Here's what happened:

A few times over the past few weeks, in our (newly installed) downstairs toilet, we would notice that the water level in the bowl was maybe half of what it normally is.  Also a smell of sewage.

Last Sunday (7/18), while running the washing machine, the sewer line backed up into the downstairs toilet, and of course we had a pretty bad mess on our hands.

Had a plumber come over the next day.  He snaked the line all the way out to the street.  About 6-8 feet in he said he felt a blockage, and when he pulled out the snaked there was some roots on it.  We figured we were OK (for now).

A few days later, I was in the basement and heard what sounded similar to a flush in the downstairs toilet, and the water lever again dropped to about half normal.  This happened as the (upstairs) bathtub was being emptied and the (upstairs) toilet was flushed at about the same time.  Now we're nervous; not wanting to have to deal with another backup, we called the plumber, he came back and snaked out the sewer line (again) out to the street.

He didn't think there were any significant blockages anymore.  He suggested it might be a venting problem.  (The downstairs "half" bath was installed last year with permits and all the proper inspections.) 

Got back from a short weekend trip to the Catskills and found the water level in the downstairs toilet less than half its usual level.

Any suggestions/ideas/help???  Thanks in advance!

Dan   
 

Did he snake from the roof through the vent all the way? Should have done so, IMHO. Gregg has the right idea.

Can you get to the external vent on the roof without falling off? If so take a long garden hose up there, push it down into the vent as far as it will go. Turn on the water. If it flows into the drain, no blockage in the vent and it's working properly. If the vent fills with water and runs out onto the roof, you have a blocked vent that needs cleaning out. Critters like to make nest in these vents. Check it out. The plumber should have done this. Is he licenced? Or afraid of heights?
Was the sewer drain Roto-rooted out. That is did he use a machine with a cutting head to remove the tree roots in the drain or just run a snake. If there is roots in the drain they need to be cut out. Again the plumber should have known this.
Call a different Plumber.

I would get a plumber that had one of them cameras and get all the vents and drain scoped

Dan,

Everyone above is on the money. You can buy an inexpensive snake yourself at any home center. I recommend getting the longest one they sell. If that is not up your alley and you may need to do this anyway... getting another plumber is a very good bet. The plumber you called did a little to diagnose the problem and basically nothing to fix it. The next plumber needs to have a roto-rooter tool. If you are up to it, you could rent one, but that depends on your skill level and how comfortable you would feel operating one. It would probably involve taking the toilet out or at least finding a clean-out.

Good luck.

Frank

PS. You mentioned the Catskills. Do you live in NY?

Thanks to all for the information.

I have contacted a different plumber who will snake out the vents (if needed). Hope that works.

Meatballkop: I live in Northern New Jersey, was just visiting friends at their house in Saugerties.

Thanks again!