Itoldyouso,
HJ is correct- overhead sewer without a pump? Pump to where is the question?
Terry is correct- Concrete is a sponge (not water tight), a Hard,Dense Sponge
Terry is correct once again - the old clay lines would unintentionally act as drain tile when a flood control valve is installed outside the house. This would keep the sewer from backing up but when closed for many hours during heavy storms would fill with ground water and in certain cases would cause and inch or two of water on the floor ( as opposed to up to 3'0" in record time that would drain as quickly when the sewer discharged)
You most likely have a bungalow, raised ranch or 2-3 flat from 1920-1960's, It had sewer back ups, to varying degrees, its entire life ( HJ comment on previous H/O sealing drains, stand pipes etc etc)- you only added a "Modified or Partial" overhead sewer-sub grade fixtures and drains to ejector pit routed to original stack and back out to original gravity sewer line.
Invert,Invert,Invert = Think in Reverse
Same combined sewer system back up coming into your basement a different route, through the floor via the new pipes and gravel bed surrounding them.
"but its clean water"- did you think or say this to yourself or others? Don't feel bad and don't add interior drain tile just yet in a 4'-5' basement, unless you live near Albany Creek, the North Branch or the Mighty Des Plaines River. The good news is your half way home- your new friend with the jackhammer unwittingly installed Phase I of your Overhead Sewer Conversion
Phase II-
A. Run stack/s out wall and then drop to existing 6" clay line and add clean out at same time-
B. When excavating A above, disconnect original exterior drain tile "T" tie in to sewer line as it exits foundation footing and run this back into basement, add sump pit and discharge to surface (not sewer stack). Surprised to find you have Drain Tile?! it was a great system, no pits,no pumps only gravity- oops! combined sanitary/storm system in a clay bowl (Chicago) we call home exposed the flaws and the danger to the homes mechanicals and the occupants safety,especially as the expectations of basements changed
Make sure that ALL Gutter downspouts/leaders tie ins to underground are sealed off.
The specifics of this plan have to due with the routing the new overhead line along the interior of the basement or exterior of the foundation wall, depending on space inside ( stairwells, windows,existing bathrooms etc) or outside ( newly placed gangway sidewalks, Peoples Gas meters,space for a machine or dig by hand etc). Use one company that carries both Plumbers and Drain Layers permits and tell your friend with the jackhammer to get back to his 24 hr shift at the firehouse!