Is a French drain between the garage and new driveway a good idea?

That mystery pipe is almost certainly a footing drain or part of an old perimeter tile system meant to keep water from building up under your garage slab. The fact that it's dripping constantly tells you there’s significant **hydrostatic pressure** under there, and the seepage through the foundation crack confirms it. If you just pour a new concrete driveway over that mess, the water will eventually undermine the sub-base or freeze and heave your new slab within a few seasons. I wouldn't just throw a 6-inch French drain between the slabs and call it a day. French drains are generally for surface water or rising groundwater, but here you already have the water concentrated in a pipe. You need to transition that crushed corrugated mess into a solid **SDR 35** or Schedule 40 PVC pipe. Corrugated is a nightmare in Michigan becuase it crushes too easily and the ridges catch silt. Since you're already tearing out the driveway, dig back far enough to find a clean section of that under-slab pipe, use a Fernco coupling to adapt it to solid PVC, and run that out to a dedicated discharge point. For that foundation crack, you've got a bigger issue if it's actively weeping. You shold seal that from the outside while the driveway is torn up using a high-quality polyurethane injection or a membrane. As for the sump pump, keep it completely seperate from your downspouts. In our winters, those downspouts will freeze solid at the exit point, and when your sump pump tries to kick on during a mid-winter thaw, it’ll have nowhere to go and back up into your house. Make sure your new concrete contractor uses a proper **expansion joint** between the garage and the new driveway, but don't rely on it for drainage. If you pipe that mystery water and the sump discharge away using solid pipe with a consistent pitch to a bubbler or daylight, you’ll save yourself alot of heartbreak. Get the water at least 10 feet away from the structure before you let it soak into the ground.

I'm worried about the depth of that solid pipe if I make the switch. How deep do you usally have to bury the SDR 35 to keep it from turning into an ice block in a Michigan winter? I've seen pipes burst before when the pitch wasn't perfect. Also, for the bubbler mentioned—does that actually work when there's a foot of snow on the ground? I'd be terrified of the sump pump burning out because the exit point is buried under ice. shoud I look into an air gap or some kind of freeze relief fitting near the house just in case?

For the freeze concern, look into an "ice guard" or air gap fitting right where the sump exits the house. It's a lifesaver in Michigan because it lets water overflow outside if the buried line ever hits an ice plug. You’ll never bury a drain deep enought to stay below the frost line here, so it’s all about that pitch.

Also, when you pour that concrete, make sure they use a thick layer of compacted 21AA stone for the base. If that mystery pipe is still weeping even a tiny bit, you want a path for that moisture to move thru the stone rather than sitting against your new slab and causing frost heave.

If you're going the pipe route, try to use 45-degree elbows instead of hard 90s wherever you can. It makes it a thousand times easier to snake the line if you ever get a clog from roots or silt down the road. Since you're in Michigan, definitely ask your concrete guy about using fiber-reinforced mix or actual rebar. Wire mesh usally just ends up at the bottom of the slab and does nothing. With that history of water under the garage, you want that new driveway to stay tied togehter so it doesn't settle and create a huge lip at the garage door entrance.