My basement sewer backs up every so often from a hole the previous owner drilled in the cast iron pipe which they used as a drain for the washer and a wash basin. The hole is 2-3 inch in diameter and is not sealed in anyway.

To me this seems stupid and probably the cause of the sewer backups because there is no longer any pressure working to get things out into the main sewer with this hole in the line that constantly lets air in and makes a nice path for the sewage to come through. I have already rerouted the washer to drain into the main stack so I would like to plug up this hole without blocking the line.

I don't care if it has a cleanout plug or not I just want it sealed since the original cleanout is another 15ft further down the line and is easily accessible. I'm glad I didn't go with my original thought of throwing a bag of cement down the whole once I realized it tapped into the line but now I have no idea what to do. Any advice or experience with this?

I hope when you rerouted the washer drain that you trapped and vented it because the opening in the sewer main was allowing sewer gas to enter your house. To seal off the hole in the pipe get a saddle clamp, (see image) and install that over the open hole. Good luck, Tom

The previous owner drilled down 2ft or so into the cement floor and tapped into the sewer line. No hookups or connections were made... just a big hole. The toilet that is upstream in the line has started to gurgle and when I turn on any faucet upstream, there are 2... in downstairs bathroom and kitchen on main level, sometimes there is a rush of air at first before the water will flow. Can all of this be caused by a blocked vent?

The washer was rerouted by my uncle who has a lot of experience and I see a trap right behind the washer and the run ends in a second or smaller main of cast iron at the very back corner of my basement which I assume has a vent but this line is where the 3 fixtures that have blowback or gurgling are connected and also the one that is 15ft upstream of my "hole" and 30ft upstream of my cleanout near my front foundation which is clear only because I opened it and plungered it. I have also had my main line snaked twice in the last year and last one was a week ago. The temporary fixes just aren't working anymore and I can't afford to spend the 4k to dig up and replace my line to the street especially if it could be something else. There is a vent directly above the smaller stack which is also above my kitchen sink so I will shine a light down there... Birds are nesting in attic vents and everywhere else they can squeeze into allong with the squirrels .