I'm running into a situation where it's increasingly difficult to bury this PVC underground 18" in some spots due to massive tree roots. Changing directions and/or destroying the roots isn't an option. The isolated roots are easy enough to tunnel under but there are root 'clusters' that are close together are the hard part. I did bore a hole in those roots about 9" deep and wanted to use rigid metal conduit, however the size I need to use (1.25") makes it difficult to source (rent, not purchase) a conduit bender capable of bending this size.

I read in the NEC table 300.5 that PVC is under 2" of 'concrete or equivalent' than it can be as close as 12" from grade. My question is: What is 'equivalent'?

Also, I tried the 'pressure water' method for tunneling, it got real messy real fast and my pipe didn't stay level, probably doing it wrong.

Looking at a few tools such as Borit as a next resort (something cheaper is ideal b/c I'll probably only use it once and I never quite get around to reselling a tool), and calling someone to finish this short portion of trench as a final resort. If anyone can offer insight as to either finishing this trench at 18", or having the PVC above that with 2" concrete (or equivalent?)

Also, one idea I just had is running the PVC and forming concrete outside the trench, and dropping it in the trench after it's hardened, hopefully that makes sense.


Tomorrow (Weather contingent) I will try shop vac'ing around the roots, OP's yard in that video appears to have some root clusters and it looks like he did an excellent job getting the dirt from around them. Patience I have, money I don't.

The difficult can be done right away, the impossible takes a little longer.

  • A worthy challenge for sure. Is there an alternate route that would work better for trenching or boring? Like along the edge of the property, even if it is four times longer than going through the trees.
    – wallyk
    Aug 19 '14 at 17:06
  • nope, it's in the backyard, and the tree covers most of it, so no matter the direction from house to garage I'm pretty certain I'll run into the same problem :(
    – MDMoore313
    Aug 19 '14 at 17:08
  • 2
    Have you considered an overhead feeder?
    – Tester101
    Aug 19 '14 at 18:16
  • No, but I wouldn't be opposed to the idea, just would have liked to not have dug this trench first though, of course ;)
    – MDMoore313
    Aug 19 '14 at 20:50
  • String up an overhead feeder, and turn the trench in to a water feature (a babbling brook might be relaxing).
    – Tester101
    Aug 19 '14 at 23:39

300.5 also specs 4" of concrete allows 0" cover (other than the 4" concrete) if it's wide enough (6" sideways from the conduit each way.) I believe that "equivalent" would allow things like concrete pavers or bricks as well as poured-in-place concrete for in-trench conduit cover.

Not sure how you approached "pressure water" boring - I'd use a section of the conduit size you want to run, or larger, with a section of smaller pipe inside it to run the water in - waste-water and dirt comes out the space between the two pipes, and the larger outer pipe directs the "drilling" - but roots and stones will stop that method, and it's not good for corners.

For tools you only need once, remember rental. But sometimes rental costs as much as having someone come do it.

I can't imagine how you'd envision pouring concrete separate from the trench to be in any way easier or more effective than pouring it in the trench. I can only see that as a complication that makes everything more difficult. Backfill and compact level with the top of the conduit, shape the trench to be wide enough for how deep the conduit is buried, pour the concrete - nothing easier than that if you have to use concrete cover.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.