Burying PVC conduit

[alanyo]

I want to bury two pvc conduit lines (1" & 1-1/4')
directly behind and against a 3-foot high retaining wall.
The conduit would be placed the required 18" below grade in
a 3" wide trench. Can I place the two lines directly on top or alongside each other ? Also I would like to place a 1" pvc water line in the same trench approx. 6" below grade and directly above the two conduit lines. (120v in the 1" conduit and 240v in the 1-1/4"). Is this permissible by code?

 

[dpc]

If you are in the US, I don't see any electrical code issues.

But better check on the water line depth - it will need to be below the frost line unless it is irrigation piping that will be drained in the winter.

 

[peebee]

Dpc is right on.

 

[advidana]

check the Nation Electric Safety Code it calls out the separation between water and power, if it does not fall into that catagory then check with the local building department.

 

[HCBFlash]

The problems as I see them, ->MIGHT<- be:

- Water 3' or deeper for frost
- Conduits interfering with possible future excavation to deal with the water line, or whichever you end up placing lower
- Conduits will move and be eventually "heaved" up by frost.
- A concrete walls foundation pushes frost deeper than ordinary, but if the wall is that of a heated building there may never be any frost for some distance from it. In the case of your retaining wall the usual depth of frost will be carried behind it, the surface of a retaining wall, as far as frost is concerned, is the surface of the ground.

Frost is not the only ground condition which should be considered, but I'm glad to see DPC mentioned it.

What you've described is (unfortunately) a very common practice, but as an inspector I'd "gig it" with such a shallow depth on your water line.

As far as codes are concerned see NFPA 70 - 300.50. Keep in mind that certain industrial occupancies may in some instances use other standards. Also most states and municipalities have specific restrictions or exceptions to "the code". The applicable, adopted, enforced version of the code shouldn't be assumed to be the latest, and in some instances there may be an entire electrical code used in place of the NEC (NFPA 70). It's been a few years since I've been back to Chicago for example, but Chicago and some other areas in Cook County IL used to use the Chicago Electrical Code (which I still prefer; the NEC has merely become a regularly updated catalog of exceptions sponsored by whichever manufacturers want to get their own products on the market).

Other than that there's not much to it... ;-)