concretedrill
The longest drill bit I have is 23.62 inches and apparently the thickness of the concrete I need to penetrate is 27.5 inches. I don't wish to buy another drill bit, is there a smart solution?
The hole is for a gas pipe to go through, so the diameter of the bit is ~1.5 inches. I am drilling into the foundation, other side ends with a thin layer of plaster.
There is a category of power tool called a multi-tool that is basically a very small saw usefull in cutting in tight spaces.
After you cut the initial hole, this tool could be used to trim away the area in the uper section on an angle to make room for your retaining arms.
The tools come in corded and cordless version, and at various price points. The are very handy and can do other things, such as spot sanding and grinding.
Your instincts sound right. Be sure the drain tube is slanted downward as it exits. Also be sure the outside end of the tube will not be blocked (by leaves, snow, etc.) and that there is adequate drainage away from the outlet site. The ground should be pitched away from the wall (as in every foundation).
The likelihood of rebar or wiring within the cinderblock is very small. To be certain, go slowly and inspect with a light as the pressure changes in drilling. There are hollow sections in concrete and cinder blocks and you should be aiming for those, rather than the webbing between holes.
Sealing should be done with a weatherproof cualking on both inside and outside.
Best Answer
A 1.5" hole (38mm) in concrete is beyond any conventional drill. You might get away drilling empty block, but not a foundation.
I'd suggest renting a big rotary hammer drill driver for this job. Most rental places are happy to rent you a suitable bit for the task as well, on the basis if you didn't have the tool you're unlikely to have the proper sized cutter.
It might also be a coring hole saw instead of a masonry twist drill, potentially with a water feed for keeping the dust down. The bigger ones come with a base that you bolt to the wall or floor to maintain tracking and not risk bending your tool's shaft.
Either way this is going to be a heavy tool to hold that is enormously loud, and will have high vibrations to the user and the structure into which you're drilling.
More info at https://www.instructables.com/community/How-to-drill-a-4-inch-hole-in-concrete/
Also, consider that you risk running into reinforcing rod (rebar) in a foundation, so your cutter will have to deal with steel as well as concrete.
Once the hole is done, you will absolutely have to clear it of dust and then seal the fresh surface - cut steel will need rust protection and the concrete will need silicon of some sort.
Consider also what other concrete holes you might want to prepare while you have the drill in your hands.
There's no shame at all in getting a contractor to drill your hole too - they will have the gear and probably cost not a lot more than a rental.