Your plumber is correct that overhead sewers are a solution. Or a lift station.

Water seeks its' own level and overhead sewers in effect raise the water table. To function correctly the plumbing must be water tight all the way from your home to the city sewer. A pump lifts water from the basement into the overhead sewer. A separate sump pump collects foundation water and ejects it outdoors above grade onto the lawn.

I lived in Mt. Prospect many years ago and had water in our basement. Unusual house, and I solved the problem with a lift station. Basically the sewer line from the house was intercepted (outside, but underground) with a large tank that contained a pump. All household waste was pumped from the tank into the sewer. A backflow check valve prevented the sewer from filling the tank.

Contact me off-line via "My Page" and tell me more about your location and problem. If I can supply info, I will.

Good Luck - been there, know the feeling.

You're correct, sewers do rely on gravity. But the only pressure is the height of the water, not like water pressure from a faucet (which is caused by a much higher "water table" created by a water tower).

If the sewer line is below a basement floor, by making a new water tight connection and elevating a new sewer line to the ceiling of the basement, the flood level is raised. All household drains are then re-routed through the new "raised" sewer. Anything from the basement must be pumped up and into the new line.

That's how they work and a raised sewer will keep a basement dry unless the entire water table height exceeds the raised sewer line.

We had some leakage in the basement due to water trapped in the flowerbeds. They are bordered with landscape timbers and held the water pretty good. I laid a piece of plastic on the beds and stopped all leaks.