I would like to run a line of outlets on the front side of my house. Ideally there will be:

  • 1 circuit of outlets that are always on for general use
  • 2 circuits of outlets that are on timers, one for Christmas lights, and the other for some hard wired light by our steps.


  1. Can I run 3 circuits through the same conduit and boxes?
  2. What kind of conduit is required for outdoor use?
  3. What is required to run the conduit underground out to my front steps?

1 Answer 1


You can use most types of conduit outdoors, though some will require liquidtight fittings. Cost wise, and due to the ease of use, I'd recommend schedule 80 PVC conduit.

schedule 80 PVC conduit http://static.hardwarestore.com/media/product/636554_front500.jpg

As long as you use the proper size conduit and boxes, you can indeed run all the circuits through the same conduit.

If you used 14 AWG THWN conductors (15 ampere circuit), you could jam them into 1/2" schedule 80 PVC conduit. If you want a bit easier pull, you could use 3/4" schedule 80 PVC conduit. If you're using 12 AWG THWN conductors (20 ampere circuit), you'll have to use 3/4" schedule 80 PVC conduit. I figured for 3 conductors per circuit (hot, neutral, ground), so that's 9 total.

If the circuit is GFCI protected, you can install the conduit 12" underground. If it's not, you'll have to go 18" deep. Since you're installing outdoor outlets, you'll have to GFCI protect them anyway. If you use a GFCI breaker, you can provide that protection, and save yourself some digging.

Wherever you go in or out of the ground, you'll want to install an expansion fitting.

PVC expansion fitting

  • See 2014 NEC 300.5 Minimum Cover Requirements Column 4 - Residential Branch Circuits rated 120V or less with GFCI protection and maximum over current protection of 20 Amps - Minimum depth requirment is 12". Also, I don't see anything in the NEC that says if the circuit is GFCI protected and in conduit then 18" is allowed. Maybe an older version?
    – Kris
    Sep 27, 2015 at 1:27
  • @Kris Sorry, you're correct, it is 12". My mistake. However, if you notice column 4 is for "Residential Branch Circuits Rated 120 Volts or Less with GFCI Protection and Maximum Overcurrent Protection of 20 Amperes". So if you want to use that column, the circuit must be GFCI protected. Otherwise you have to use column 3, and it would be 18". I was going from memory, and my memory is failing.
    – Tester101
    Sep 27, 2015 at 1:40

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