I am installing a tankless water heater and need to drill a 7" round hole through an 8" concrete foundation wall. The location is remote and no pros will come out for less than $400+ so I need to do it myself. I plan to drill 15 to 20 3/8" holes with a heavy duty rotary hammer and then sledging the plug out. Anyone have other ideas that would work for me I'd love to read them. Thanks,
Bob

Try to rent a core drill

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7" Bits

Diamond Core Drill Bits | Cutting Concrete | Cutting Asphalt

That's KISS but with that bore costing over $300 plus renting the rotary hammer I'll be even higher than playing a pro. I appreciate the offer but I hoping for a magic bullet that hasn't come to mind. 20 3/8" holes in a circle can work but its not going to be fun. Speedball1 suggested I cut with a circlar concrete saw making a square hole and then grouting the pipe in later, also a possibliity.

This is poured concrete? For block I use a big hammer and fill back in with mortar.

Some rental yards have core drills. Just bolt the base to the wall and let her rip.

Bob
Recently helped install a few radon gas elimination fans.. 7" hole through the concrete slabs in basements and used your method .. granted I only went through slab thickness 4-5" but it worked well.. Only downfall took some time to drill the holes.. but once the pipe was in and all was grouted looked good..

Thanks Labman and Pelle. It is a full 8" poured wall so I won't have gravity on my side either. HD only rents up to a 6" core but I have now found another place that has 7" and 7.5" to rent. The rotary drill is 50 lbs so I'm thinking of hanging a sling from the joist just to carry the weight so I won't spill my beer. I have seen the coring machine that hangs from the wall, glad you mentioned that option. Just can't see paying a pro $400 for this kind of low skill grunt work. I can grunt pretty good. Thanks gentlmen.

Naw, all you do is hammer drill a 3/4'' hole and put an anchor bolt in the base of the drill. I actually have worked as a core driller.

The rotary drill is 50 lbs so I'm thinking of hanging a sling from the joist just to carry the weight so I won't spill my beer. QUOTE]



Hanging is a good idea, I would also look into someway to use a hyd. Bottle jack to do the pushing on the drill, a couple of saw horses and few boards blocked to the nearest wall should make your beer drinking easier. Lol

It helps to have somebody else hold the drill while you tighten the bolt. Once bolted in place, you hold the drill feed knob in one hand and the beer in the other. Whoever held the drill may need 2 beers.

Don't forget dust mask and ear plugs. Cement dust is surprisingly bad for your lungs.

Too bad you couldn't get a concrete coring guy out. Sometimes it helps if you talk to the individual worker rather than the office. I had one do an 8" hole through a 18" poured retaining wall for $150 cash & a beer

Thanks you folks for some great suggestions. The job is locatted at the intersection of Illinois, Iowa and Wisconsin not near any real town. The two guys who are willing to come both want around $400, primarily due to the travel time. Labman's wall hanging core machine will do it if I can find one to rent.

Yes, business once took me to Dekalb Illinois. When we exited the Interstate, we were almost picked clean, and didn't have enough change for the last unmanned toll booth. We drove away red lights flashing. Likely now the thing takes dollar bills.

Went to college in Dekalb, you were lucky to get out alive. That booth wasn't there when I went to school but it showed up during grad school. We blew past it back then with no cameras or troopers around. My only illegal act.

Hey bob, what you were saying about drilling the 15 to 20 holes is what I've always done in the past, it works. And to be honest I never thought it turned out that bad.
Once you get it drilled id go on the outside and tap it with the hammer till it broke though, you can make it fairly neat by just tapping it. Good luck