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I have a 2nd story porch that I want to put lights under.

I'm not sure whether EMT or PVC will be more durable in the long run. It will get both rain and some sun, and I'd like it to last a long time.

What's more long lasting ? Will the EMT rust over time ?

  • Can you pick a path for the conduit so it is out of the sun and rain as much as possible? – Criggie Apr 18 at 0:02
  • Yes, for the most part. There are a few areas that will get some sun. – joseph.hainline Apr 21 at 0:03
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Steel EMT will rust over time in a buried environment with moisture where PVC will last virtually forever unless it's exposed to sunlight.

I'd go with PVC which is also likely to be less expensive.

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    To use EMT in a wet location weather tight fittings are also needed. PVC conduit is available in UV resistant types. Agree go pvc. – Ed Beal Apr 17 at 15:35
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    I don't think the OP will bury them, no more than under a roof structure, since it is a porch and not a deck. The gray PVC conduit is the way to go.+1 – Jack Apr 17 at 15:43
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    Also, if the conduit is "subject to physical damage", make sure it is schedule 80: diy.stackexchange.com/a/121452. You may have to go to a dedicated electrical supply shop to get it (most big-box stores in my area don't carry it). – statueuphemism Apr 17 at 15:52
  • Actual electrical conduit PVC is (all? every stick I've ever bought, anyway) "sunlight resistant" - but you caould also paint it if you wanted to, I guess, which is a common approach for non-sunlight-resistant plumbing PVC among people who don't just put that in the sun and act shocked when it breaks. Anyway, I use EMT inside and PVC outside as a rule. At the moment the PVC is about 2/3 the price of the EMT in my local market, but that varies. – Ecnerwal Apr 17 at 17:04
  • Please note that I did not say that PVC, in particular the "sunlight resistant" kind could not be used in sunlight. I said, in comparing it to steel, that it would last forever if buried. Even the sunlight resistant PVC does break down in sunlight over time but steel does not. – jwh20 Apr 17 at 17:12
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EMT has the merit of being protected from physical damage, but it will rust and requires special boxes and kit to prevent that.

PVC Sched 80 is also protected from physical damage, and, you can use Sched 80 and Sched 40 interchangeably (since the critical dimension, the OD of the pipe, is the same).

PVC conduit will degrade in the sun. It's sun resistant, but that only applies until the warranty expires :) Your best bet is to scuff-sand it with some 3M green Scotchbrite pad, then paint it with an alkyd primer and normal house topcoat.

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  • You know there are code restrictions on plastic under buildings...I’ve heard. – Lee Sam Apr 18 at 0:03
  • So, run the PVC inside a larger diameter EMT! – Hot Licks Apr 18 at 1:34
  • @LeeSam -- there's no "under buildings" line in NEC 352.12... – ThreePhaseEel Apr 18 at 14:56
  • @ThreePhaseEel I was thinking under foundations...not “inside” per se. – Lee Sam Apr 18 at 22:41
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Aluminum EMT is available. Check with your local electrical supplier. If you feel that the higher cost is worth it, you'll know that it won't rust and is unaffected by sunlight.

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