Tunnelling under sidewalk/walkway

chippate(z7 NC)July 7, 2005

Although this is not an irrigation-related question, per se, I thought maybe some of you experts could offer some suggestions.

I am installing some low-voltage landscape lighting and need to route some of my wiring under a concrete sidewalk that wraps around the side of my house to the back of my house. I've read that the best way to accomplish this is to dig a trench on either side of the sidewalk, and using a pipe and a water hose, push the pipe through using the water to dig through the earth under the sidewalk. What I've seen suggested is to use a metal pipe that's threaded on one end with a hose adapter. Unfortunately I've had no luck in locating a source for the metal pipe and, in fact, various contractor/plumbing suppliers have looked at me like I was crazy when I explained what I was trying to do. I'm inclined to believe this is a fairly common problem that irrigation system installers deal with everyday. Can anyone out there suggest how I can either do this a different way or suggest where I can purchase the materials I need?

Thanks in advance for your help.


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I am generally fortunate enough to be able to sleeve prior to the pouring of sidewalks or installation of driveways. In those few instances where I did have to go under existing sidewalks I either contracted someone with boring equipment and let them deal with it or dug trenches as you described and drove a pipe under the sidewalk with a sledgehammer and pulled it back out; then pushed my irrigation line through the hole I just created. It was sandy soil and did not take much effort. As for the adaptor you are looking for to go from 3/4" female hose thread to 3/4" npt they are readilly available at most irrigation suppliers, have seen them at the big orange box; too bad your not closer as I have several in my shop at this moment.

good luck

    Bookmark   July 7, 2005 at 4:37PM
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dmullen(Southern CA)

I use 3/4" PVC with a hose adapter glued on one end and the tunneling nozzle that is made for this purpose. Home Depot and Lowes have them and so would any store that carries PVC.

    Bookmark   July 7, 2005 at 11:06PM
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It is indeed a common task ....

Side walks and driveways up to 15 feet can be penatrated with standard tools ...

If you want to use water under pressure ( a great technique ) use PVC pipe there is no need to use expensive metal pipe ... hookes to your garden hose with a jet type nozzle will give you all the pressure you need.

First .. start by slecting where you will go under the sidewalk ... make sure you have as much room as possible on both sides .. and take a look around to get an idea of what the root or stone situation might be under ground. Try to pick the best spot. ( By the way be certain going under the sidewalk is the only route !! )

Second .. try to dig rectangular holes on each side .. getting as much room to each side of the sidewalk as you can .. up to the length of a shovel .. so you are digging level. Keep track of your position and progess by marking distance on your shovel or other digging tools. Don't be in a rush to dig under the sidewalk until you dig out and down on each side .. the first holes you make will save a lot of work.

Third .. all is fair in love .. war and going under sidewalks .. a digging bar is a must .. trenching shovels .. hammers ... boring tools .. whatever works .. pressurized water works very well.

Fourth .. repack the soil carefully under the side walk or in time you may end up with a caved in walk way.

Lastly .. remember the "impossible takes a little longer" .. George Santiago said that ..

Good Day ...

    Bookmark   July 8, 2005 at 9:50AM
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Agree with most above. Use PVC not metal. It bends a little so your dig out doesn't need to be perfect, and it's cheap. Obviously make the PVC pipe a little longer than the concrete is wide if you plan to work from one side--just a little more than half if working both sides. I prefer one side as it concentrates the mess, and you excavate less to make room to work.

Don't buy a special nozzle. Just get a PVC cap for the pipe and drill a small hole in it, or better yet, 2 hole in different directions.

Another trick I found that worked well was to hook up a length of PVC to my shopvac. Blast for a while, shopvac for a while. It worked wonders at clearing the hole.

Final tip, whenever laying concreate, plop in conduit even if you don't know if you'll ever use it. I've save myself a lot of energy by this simple, cheap, yet paranoid behavior.

    Bookmark   July 8, 2005 at 3:30PM
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hookoodooku(8a AL)

There are some situations where water pressure from a garden hose WILL NOT BE ENOUGH. I've got heavy clay soil with lots of rock. The only water pressure that's going to work here is a pressure washer. With a pressure washer, I was able to make quick time in drilling out a hole for a 4" PVC Sleeve going under a 5' wide sidewalk.

Another cheap trick that can work (especially if all you need to do is install a wire) is to "drill" a hole using a piece of rebar. While I won't claim that it was easy, I was able to run wire for an irrigation system under an 11' wide driveway with a 15' piece of rebar and a 3# sledge hammer.

    Bookmark   July 8, 2005 at 3:43PM
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dmullen(Southern CA)

I forgot to mention another advantage of PVC. It is easy to start with a short piece and then add on as you go through. Makes it easier to handle than a single 15 ft long piece.

    Bookmark   July 8, 2005 at 6:24PM
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Perhaps you could rent an Air Spade. It is used with a compressor to remove soil from around a tree without damaging the roots. Google for more info.

    Bookmark   July 8, 2005 at 9:51PM
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On older concrete work you can sometimes lift the entire slab up and away and dig your trench ....

Good Day ..

    Bookmark   July 9, 2005 at 10:27AM
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I just did it again. I use the water hose (and a 3 ft PVC pipe) and got it almost thru. Then I use the water pressure hose, oh boy, it get thru in seconds, not minutes.
During my new sprinkler installation (with some digging), I found that there were another PVC pipe previously installed under the concrete pathway about 3 feet from where I put my new one thru. Hmm... at least I learn that the pressurized water hose work best for this.

    Bookmark   July 11, 2005 at 1:37PM
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andy_mayfield(z6 md)

if its just under your sidewalk...a lot of garden centers sell garden augers. not the big suckers for drilling large holes for planting trees. the ones that make a hole about 2 or 3 inches wide. they can be 3 feet long and attach to almost any drill. run usually about $20. so if your sidewalk is less than 6 feet wide, a 3 foot auger will work just fine

    Bookmark   July 15, 2005 at 7:31PM
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blip01(7, NJ)

I recently went under 2 different areas of sidewalk. Once running wire to my sprinkler valves, and the other running a sprinkler head out to the grass strip between the sidewalk and street.

I think the most important bit of advice is to dig your trench big enough, and deep enough at the start. Dig it at LEAST as long as the pipe you're using, plus enough room to swing a hammer/mallet to drive it through. trying to skimp on the digging portion will make the job a real pain, trust me, I know. :-)

    Bookmark   July 18, 2005 at 9:11AM
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After reading the posts on this site, I attempted to tunnel under a 4 ft wide sidewalk with a nozzle on the end of a 3/4 inch PVC pipe. Unfortunately, there was a lot of gravel under my sidewalk and all I managed to do was create a big, wet mess! So, here is what worked for me. First dig down 10 inches to a foot on either side of the sidewalk. Then continue to dig back on one side (whichever is easier) for 5 ft (one foot more than the sidewalk width). I purchased a 4 ft length of galvanized 3/4 inch pipe threaded at both ends (about $16). On one end, I screwed on a 3/4 inch by 1/2 inch bell reducer and then a 4 inch by 1/2 inch nipple. I hammered the end of this 1/2 inch nipple so it was practically pinched closed. When screwing these fittings together, only tighten hand tight onto the 4 ft pipe - you will be removing them later. This end with the 1/2 inch nipple will be the "point". On the other end, I screwed on a 3/4 inch coupling - it provides a sturdier surface for hammering. I placed the pipe into the 5 foot trench just below the sidewalk. Using a regular hammer, I tapped the point into the dirt under the sidewalk until the end I was hitting stayed up on it's own. Then I started hitting the pipe with a sledge hammer until the point came through the other end. Then I removed the bell reducer and 1/2 inch nipple and flushed the pipe with water in case any dirt made it through the end of the 1/2 nipple into the pipe. The thing I like about this method is I didn't washout a big area under my sidewalk. This worked for me - I hope it works for you!

    Bookmark   February 18, 2008 at 8:01PM
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sanram324 AND ALL OTHERS

    Bookmark   January 22, 2009 at 12:23AM
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I want to put a 5" drainage pipe under my sidewalk. I plan to buy a length of similar sized PVC and blast water into it. The mud should drain back out of the PVC as I go, and hopefully the hole I make will be the right size and uniform. I think I can get through the Georgia clay, but there are also granite rocks in the clay. I can try rebar on them.

    Bookmark   June 29, 2009 at 5:30AM
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Actually it is 4" Corex pipe. I dug my pits and took a sample of the clay under the sidewalk. I blasted it with a hose and it WOULD NOT DISSOLVE! I doubt that a pressure washer could cut through it. Home Depot had nothing to buy or rent that would help me EXCEPT an underground valve turning tool. I'm going to pound & twist my way through from each side. When I'm done I will pack each side with QuickCrete to prevent washout and help support the sidewalk.

    Bookmark   June 30, 2009 at 1:34PM
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