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Thread: How do I enlarge an existing hole through concrete block?

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    Default How do I enlarge an existing hole through concrete block?

    I've got a 1 1/4" galvanized pipe for my sump pump drain going through the concrete block in my basement.

    I just put a new, much larger pump in and I want to run 1.5" pcv out through the block.

    Aside from chiseling and patching, how can I enlarge the hole from the 1.75" it is now to 2" so it will fit the pvc?

    I'm used to wood hole saws which require a center for the pilot bit. Without a center, your hosed.

    What equipment would be needed to create/drill this new hole?

    And then, similar to another recent post of mine, how do I secure the pipe from sliding in and out of the hole? Is there some sort of clamp that would secure it to the wall?

    Thanks.

  2. #2
    DIY Senior Member Marlin336's Avatar
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    Without getting into real expensive tools (a core drill, or a hilti) you're pretty much limited to filing or chiseling. If you can find a hole saw you get your center by cutting a hole in a piece of 2*4 the same diameter as your bit. Hold the hole in the wood over where you want to drill, hold the wood tightly (better with a helper) and drill, the hole in the wood will act as a guide and keep the bit from wandering.

  3. #3

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    Is a 2" concrete hole saw something I could rent from Home Depot or any other type of place?

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    DIY Senior Member Marlin336's Avatar
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    I've never seen one long enough to go through a foundation that attaches to anything but a core drill. You can probably rent one but a core drill is heavy and large and is really supposed to be bolted to the wall you're drilling although a couple guys could probably work it for a 2in hole. They cost a couple thousand dollars but you could probably rent one.

    You could also probably find a diamond hole saw for a grinder but it's only going to be a couple inches deep. You'd have to drill the first 2in or so on each side with the hole saw, chisel out what you drilled (you have to chisel it but it will give nice lines because of the hole you drilled) then just chisel away at the inside part. That's probably your best and most economical bet if you can find the bit.

  5. #5

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    I just went through a similar ordeal: I bought a concrete drill bit, chucked it in my 3/8 variable speed drill, and drilled a bunch of pilot holes. I then used a garden variety chisel to break the concrete. It took a while to do all this, but it worked fine for my purposes.

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    Plumbing Designer FloridaOrange's Avatar
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    As long as there's no reinforcement in the immediate area, filing the concrete may be easier than you think. A concrete file can make short work of that, as you're only increasing the size a little bit.
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

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    General Contractor Carpenter toolaholic's Avatar
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    Default No brainer

    Go to the rental yard and rent a rotohammer. Get a chisele bit , and a couple of 1/2" drill bitts. If one gets stuck,release it from the chuck ,put in another and drill the stuck one out. Also pipe wrenches work well to back out stuck ones. Get at least 12" long bitts

  8. #8

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    you could rent a core bit and hammer drill from home depot... cost you about 16 dollars for four hours... it will take two minutes to do it.

    however for that...i would drill smaller holes in a circle, then chip away...

    i used the core driller to drill a new hole for a toilet.... was neat and clean..that had to go through 4 inches of concrete, however.
    Last edited by lee polowczuk; 08-22-2007 at 11:12 AM.

  9. #9

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    Thanks. I'll be checking Home Depot Rental.

    If necessary, I could machine a "plug" that would be two diameters and used as a pilot for a core drill. 1.75" on one side to fit nicely in the existing hole, and another diameter to fit inside the core bit. That would allow me to at least start the hole. After a while I could remove the plug and let the new hole guide the drill.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    I'd just probably drill a bunch of smaller holes, and chisel it out. Then, put the pipe through and maybe use hydraulic cement to seal it up. I think you mentioned a block wall. That should grind off fairly easily with the right stone or file...your hole doesn't need to be much bigger. Seems like overkill to rent a coring drill. If it is a poured concrete wall, maybe, but I think I'd still try to drill and or chisel it.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member rerod's Avatar
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    I realize this is a old thread.. But I need to drill this same hole, except through 10" of poured. Maybe I should rethink this and go up through the ceiling and out in a joist space instead.

  12. #12
    DIY Senior Member BobL43's Avatar
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    Quote Originally Posted by mckeand13 View Post
    Thanks. I'll be checking Home Depot Rental.

    If necessary, I could machine a "plug" that would be two diameters and used as a pilot for a core drill. 1.75" on one side to fit nicely in the existing hole, and another diameter to fit inside the core bit. That would allow me to at least start the hole. After a while I could remove the plug and let the new hole guide the drill.
    I have use diamond dust hole saws to drill holes through extremely hard porcelain floor tiles with no problem at all. A cement block should be a piece of cake to go through using your idea of a wood plug for the center point to get it started, which is the only time it would be needed. Once the saw starts cutting through the concrete, it will most likely be able to guide itself. This should do the trick, plus the arbor setup, fo rnot too much money. Just spray some water on the area as it being drilled. http://www.zorotools.com/g/00052794/...FQVU4AodASYA6w this is a 2 inch diameter, which should fit a 1.5 inch PVC pipe perfectly. And yes, you will have to do it from both sides, I guess because the block is 8 inches thick, although you will need to drill through only about 1.5 inches or so total, unless you are drilling through one of the webs
    I am definitely not a pro plumber, but I am a pro crastinator

  13. #13
    DIYer, not in the trades LLigetfa's Avatar
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    BobL, Do you realize you are replying to a post from 2007? If the OP has figured it out by now, I doubt he ever will.

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