How do I enlarge an existing hole through concrete block?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by mckeand13, Aug 21, 2007.

  1. mckeand13

    mckeand13 Engineer

    Messages:
    68
    Location:
    Milwaukee, WI
    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. TMB9862

    TMB9862 New Member

    Messages:
    206
    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. mckeand13

    mckeand13 Engineer

    Messages:
    68
    Location:
    Milwaukee, WI
    Is a 2" concrete hole saw something I could rent from Home Depot or any other type of place?
  4. TMB9862

    TMB9862 New Member

    Messages:
    206
    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. kirwin2

    kirwin2 New Member

    Messages:
    4
    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.
  6. FloridaOrange

    FloridaOrange Plumbing Designer

    Messages:
    1,317
    Location:
    SW Florida
    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.
  7. toolaholic

    toolaholic General Contractor Carpenter

    Messages:
    874
    Location:
    Marin Co. Ca.
    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. lee polowczuk

    lee polowczuk New Member

    Messages:
    63
    Location:
    Florida
    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: Aug 22, 2007
  9. mckeand13

    mckeand13 Engineer

    Messages:
    68
    Location:
    Milwaukee, WI
    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.
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,801
    Location:
    New England
    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.
  11. rerod

    rerod New Member

    Messages:
    13
    Location:
    Iowa City
    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. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,826
    Location:
    NW Ontario, Canada
    No kidding, and not even related. The OP had a hollow concrete block to go through, not 10 inches of solid concrete. Even so, some of the advice given was not related to just hollow concrete block. The core drill method would work well if the existing pipe can be removed.
  13. Terry

    Terry Administrator Staff Member

    Messages:
    14,753
    Location:
    Bothell, Washington
    With an old 10" concrete wall, core drilling sounds like the easiest method.
    Working it with smaller holes and chiseling works too, but what a pain.
    Someone with a core drill would knock that out in no time. And you can have coffee while he's working.
  14. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,230
    Location:
    Cave Creek, Arizona
    There are "hollow core carbide bits" that work in a conventional 1/2" drill motor. They take some "push" and are not inexpensive, but neither are core drills which are seldom "rented" because you can destroy a very expensive diamond bit in a matter of a few seconds if used improperly. There was a plumbing company in Chicago, many years ago, which decided to buy its own core drill and bits rather than hire a company to drill a multitude of holes through a concrete floor. When they discovered that they were using 2 or 3 bits per hole, they sold the equipment and hired a professional driller who did the entire job with one bit.
    Last edited: May 6, 2013
  15. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,786
    Location:
    Long Island, NY
    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...kw={keyword}&gclid=CJqO9a_ngbcCFQVU4AodASYA6w 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
  16. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,826
    Location:
    NW Ontario, Canada
    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.
  17. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,786
    Location:
    Long Island, NY
    LOL! Guess I have to read more carefully. What through me off was that you, HJ and Terry all replied, but it was about the solid 10 inch wall that rerod spoke about. Duh!

    Threw, not through. to, too, two, three more words that sound the same, but are soooo different
    Last edited: May 6, 2013
  18. Terry

    Terry Administrator Staff Member

    Messages:
    14,753
    Location:
    Bothell, Washington
    We responded to this recent post about the 10" wall.
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