Need help with drilling a hole in my wall to install a radon system

[telecast]

Hi, this is my first time posting. Wasn't quite sure which forum to post in so I hope this is ok. My question is that I'm installing a radon vent pipe and fan to run from my sump pit (which I'm going to seal) to outside the house. I'm drilling through cinder block and then through brick to the outside of the house. I rented a hammer drill and a 4.5 inch drill core bit from a local hardware store. The pvc pipe I purchased to run through the hole has an external diameter of 4.5 inches. I asked the guy if that would be too tight a fit, and he said no, it should be fine, since he had recently done it himself with the same size pipe. Well, it didn't work. I drilled the hole, but I can't even get the pipe in the hole.
Fortunately he refunded me, but now I need to figure out how to get the hole bigger. Because of various issues in my basement, this one spot really is the only place I can run this pipe without running into complications. If I rent another hammer drill with a five inch core bit, will that work to enlarge the hole? I'm concerned because there won't be anything for the guide bit to bite into, since I'm enlarging a hole I've already drilled. Think I'll be ok?
Thanks!

[FatimaandAhmed]

Hi! It sounds like you're dealing with a tricky situation. If the 4.5-inch hole you drilled is too tight for the 4.5-inch PVC pipe, then using a 5-inch core bit should help you get a better fit. Renting a hammer drill with a 5-inch core bit should indeed enlarge the hole, but you’re right to be concerned about drilling into an existing hole.

Here’s a friendly tip: When drilling out an already-drilled hole, make sure to go slowly and carefully to avoid damaging the surrounding material. If possible, use a bit with a guide or pilot bit to help keep things centered. You might also want to ensure the bit you rent is designed for enlarging holes and is sharp enough to handle the material.

Additionally, if you find that the 5-inch bit still doesn’t fit well, you could try using a rotary tool or an oscillating multi-tool with a grinding attachment to carefully widen the hole further. Just take your time and work in small increments to achieve a snug fit for your pipe.

Good luck with your installation!