Not to be critical, but to me, your post doesn't quite make sense. Tree roots can cause a sewer backup - but to say the basement was 'flooded' - that doesn't make sense.

Speak with your neighbors and find out what was the cause of their problem. Did they actually have their sewer lines replaced? From their home to the street?

Hi, It looks like my second door neighbour had a bathroom renovation. All others had their sewer lines replaced from their home to the street, and had a dumpster full of construction debris in their front yard. A plumber spent several days there. That's why I assumed they had their basements flooded from sewer backup. No trees were in the vicinity of their sewer line nor was any tree removed after their problems occurred.

I don't know these people, I think it would be strange that I go knocking at their door to inquire about their sewer problems. So what can I do to be proactive?

You are jumping to a lot of conclusions with little hard info. Before worrying and taking precautions, go meet your neighbors and see what is going on. And just because a few neighbors have had sewer problems -- or you think they did -- doesn't necessarily mean anything for your situation.

"What's really sad is that they are your neighbors, and you haven't ever just said hi?"

Well, for the first part, they live further down the street, maybe 20-22 houses down to be more precise, so they're not really close neighbours, and for the second part, I work on evening shifts, leaving home at 2 o'clock and I come back usually around 12:45, so when I leave they are still at work and when I come back they're probably sleeping. When they are home in the morning then I'm sleeping. I did however speak with my second door neighbour, who confirmed he really just renovated his upstairs bathroom.

Also, It is pretty obvious they did have sewer problems; I have seen plumbers replace their sewer lines from the street to their houses, and lots of drywall, flooring and carpeting went into dumpsters. On two houses, the city even got involved and parts of the street were opened up to perform work down below.

So, I might be wrong, but I think it's safe to say there's a 90% chance if I go see them, if they don't tell me to fly off, they will tell me they had sewer problems. Perhaps I could try to get a hold of them during weekends and ask them about the specific reason why they needed the work done, but I thought someone on this forum might already have a clue.

I will however ask one or two good plumbers for their opinions.

My neighborhood is ~60 years old and yes, the sewer lines are all being replaced. They were made of the stuff that apparently lasts ~60 years in our environment ("Orangeburg" pipe I think). We don't have basements so the first sign of failure is gurgling toilets and slow drains.

Talk to your neighbors (sewer talk is a great way to meet people!), talk to the city and ask if there have been problems, talk to a plumber with a scope, and keep an eye on the lowest drain in the house. You shouldn't get enough backup to destroy stuff if you're paying attention, and you are!

You can pay a plumbing company to send a camera down your line and see what condition it is in. The only thing is the last time I had this done it was kind of expensive. But I had been told in the past my tiles were failing and the last time they said they were turning to gravel, would deduct the cost of the camera work from a line replacement - so I went ahead and did that.

Although because it cost thousands to replace the line, as my house is in the upper part of 8/10 acre resulting in a comparatively long line - I actually wasn't going to agree to the project until they offered me credit through a third party.

If it takes me the whole 10 years the creditor allows to pay it off the interest is going to end up doubling the cost of the work.

Of course when a sewer line fails suddenly, resulting in delights like toilets vomiting onto bathroom floors there can be additional thousands in repair costs on top of the cost of the line replacement. And the hassle of going without plumbing until the line is replaced.

Backflow prevention only helps if the street main gets backed up, and you also have to stop using water once you notice it. Pretty much if the drain line fails anywhere and the backflow prevention is working, any water you use will end up in the basement because it has no where to go, however the backflow stops neighbor or city sewage from entering your basement. Best to have a floor drain in the basement with a watchdog to alert you if water is backing up so you stop using water.