I'm running some electrical wire around where I'm building my house. There are two places that I'd rather not dig through: A driveway and a creek. The creek is the most important, because the state will require me to get a special permit, dam the creek, and temporarily redirect the flow before it will allow me to dig through it. Ick.

As a result, I'm going to use directional boring (a.k.a. horizontal directional drilling or HDD) to go under the driveway and creek. That way, I never have to disturb the creek bed or dig up the driveway. However, I'm a little uncertain about what type of conduit is permitted to be run through this directionally bored hole.

The only thing I can find in all of the Codez is this, in 300.5:

(K) Directional Boring. Cables or raceways installed using directional boring equipment shall be approved for the purpose.

In all my Interwebz searching, HDPE is clearly approved for directional boring use. However, I've called every electrical supply store and warehouse (that will deal directly with clients, as opposed to only retail outlets) in a 60-mile radius, and none of them sell HDPE conduit. Some of them can order HPDE conduit, but only in huge reels, and they won't sell it to me by the foot. I have to buy the entire reel (2000 or more feet). I only need to bore for 30 feet under the creek and 30 feet under the driveway!!!

So then I take a look at my PVC conduit. The Codez says PVC conduit shall not be used in areas where subject to damage, except when approved for such use. Schedule 80 is commonly used under driveways and roads because that's considered "subject to damage." Both my Schedule 40 and Schedule 80 say they are approved to conform with UL 651. I can read the scope for UL 651, which says (in part):

1.2.4 In addition to the applicable requirements specified in this standard, Schedule 40 and Schedule 80 rigid PVC conduit intended for directional boring shall be subjected to the performance requirements in 6.12.

However, I can't read 6.12 because you have to pay for it ($$hundreds to thousands$$). It sounds like complying with 6.12 may be an optional part of the standard, but the conduit doesn't say that it conforms to some part of the standard and not others, just that it conforms to UL 651.

So there you have it: I'm not sure what to do. Can I just put Schedule 80 PVC conduit through this directionally bored hole?

2 Answers 2


I don't know what regulations allow, but I have never seen horizontal boring done without installing the HDPE flex conduit as part of the process.

They bore by pushing the bit forward until they hit the destination. Then they swap the boring bit for a pulling end, and pull the conduit back through the hole as they are removing the drill rod. There is no separate conduit installation from the boring; you can't realistically push conduit through the bored dirt afterward.

How are you planning on doing the boring? Is this something you are going to jerry-rig yourself, or hire a company to do? If you are hiring it out, they likely will have some leftover end spool. As you say, 30 feet is a small fraction of the 2000ft spool. It should not be hard to get that as leftovers from the boring company, I would think.

And if you are doing it yourself, perhaps you can still buy some end spool offcuts from a boring company.


You can purchase HDPE online from McMaster-Carr in a wide range of ID sizes (3/4", 7/8", 1", 1 1/4", 1 1/2", 1 3/4" and 2"). The material is Semi-Clear White and is available in lengths of 10, 25, 50 and 100 feet.

The tubing is specified for use with compression fittings (also available from McMaster-Carr) and supports a usage temperature range of -100F to +180F.

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