PVC conduit. Really necessary?

[sherab]

Hey folks, I am grappling with a decision right now regarding my electric. The power company says that I can go 18 inches down if I have the lines encased in conduit or 24 inches down for bare burial. The difference being that if it's bare burial it has to be encased in sand.

Here's the problem: the cost of PVC. Thanks to the cost of oil PVC Schedule 40 conduit in my area runs about $5.30 a foot! I am running 400 feet of line and as you can see the cost is really starting to jack up with just the PVC running $2K. I'm building 400 feet back into the woods so running electric via poles isn't an option due to the ungodly number of poplars that I have that fall over.

The argument made by my electric guys is that due to the loose shale in the soil there's a chance that my lines might get severed or if there's a problem later they'd have to dig the line up.  I do have rocky soil, it's central NY and we have an abundance of loose shale and clay.

A plane might fly into my trailer too, but there's the issue of likelihood. If you bury 2 feet down and have the sand bedding, is this enough? How necessary is the PVC?

Julian

[JRR]

Since they give you the option of direct burial, I'd go with that ... unless the additional digging depth and the sand is an offsetting cost issue.  Someone once told me that direct burial results in better heat transfer into the earth ... don't know if this is true, or even important, but apparently some folks think it is.

[glenn-k]

I don't think there is too much difference with the PVC.  A good backhoe operator may feel it if digging but that is not the way to do it anyway.  It should always be hand located if you are going to dig near it.  Ask me -- I know - I've hit lots of things.

Considering the cost I would want to use the sand and wire.  Installing a locating wire or some means where you could find it yourself would be nice also.

[John_C]

I'd bury it, but a good bit deeper than 2' if it's close to a traffic area.  

When I buried mine 20 years ago it was recommended I go down 5' since some of it ran under the gravel driveway.  The argument was that traffic, freeze-thaw etc would cause movement of the dirt and rocks around pipes and wires buried in a more shallow trench.  I hired a ditch witch to dig them and it wasn't much more of a project to go down the recommended 5'.   Some of my neighbors who did a more shallow trench have had recurring problems.  I'm in the N GA mtns. and have rocky, clay soil.  Probably less freezing issues than you have.

I'd love to hear other folks opinions on going deeper.

As always YMMV

[glenn-k]

Good point, John C.

Our direct burial used to be recommended at 4 feet min.

I have owned 2 Ditch Witch R65's and when contract trenching many times put it down to the 4 foot min.  There is much less concern about hitting it when doing future work if it is that deep.

[MountainDon]

The capacity of electrical cable is reduced when running it through any type of conduit as there is more heat build up when encased.

Taking it all into consideration I'd go with whatever costs less... and deeper can be better. You never know what digging the future might bring.

[Rover]

When burying electrical lines, I've laid old lengths of lumber in the trench approx 6" above the wire.  It should be seen if you go back to dig.  Sometimes I've used that red marker tape instead of lumber but I don't know its life span underground.
It also helps to have accurate as-built drawings.

For my future place, I've had the idea of burying the power under the road.  In that way easy to remember where it is and should be cheaper than trenching in virgin area and after restoring the site surfacing.  Anyone see any problems with this?

[glenn kangiser]

The red marker tape  should last near forever underground.  It takes UV to deteriorate plastic. That's why it is a problem in landfills and why it is a good underground waterstop.  Sounds like a good idea.

[Okie_Bob]

Wondering if the electric inspector has mentioned that you need different type of wire if you are burying vs laying in pvc? I'm not sure but, believe if you are direct burying you need a much more expensive wire. And wire is a LOT more expensive than pvc. Also, I sure am glad I got my plumbing finished before the pvc price went up. Wasn't even aware of it!
Okie Bob

[MikeT]

Your prices for Schedule 40 PVC are much, much higher than I just saw last night.  I was at HD and a 10 foot piece of 3" Sched 40 runs $10.50 here in Portland, OR.  I would have a hard time believing that prices are 5x that elsewhere.  I only have 80 feet to trench, not 400, and I might have a 36" 90 degree sweep or two involved but that is it.

mt

[sherab]

You are right! Call it naive but it's been my experience so far with my contractors that they are marking things up to a ridiculous degree. Now when I get a contractor quote I triple and quadruple check it. So far I have systematically crossed several contractors off my future business list.