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#74734 - 04/28/04 09:39 PM PVC Schedule 40 or Schedule 80?
tom07 Offline
Handyman

Registered: 04/19/04
Posts: 693
Loc: Massachusetts
When running wiring to a detached outbuilding I have the impression that the bit of PVC exposed above-ground that goes into the LB box should be schedule 80, but that the below-ground stuff (buried to 18") can be schedule 40.

Is this correct?

Schedule 80 seems to be hard to find at the DIY places so I was hoping to do it all with schedule 40, but if I can't I will find a way to get the schedule 80.

(Added later) Also, is PVC schedule 40/80 pipe the same as PVC schedule 40/80 conduit? DIstributor web sites are confusing on this point.

Thanks,



Edited by tom07 (04/28/04 09:54 PM)
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#74735 - 04/28/04 10:27 PM Re: PVC Schedule 40 or Schedule 80?
Arnold Offline
Helpful Electrician

Registered: 07/09/02
Posts: 5000
Loc: United States
Yes, you are correct. It is typical to use schedule 80 above ground and schedule 40 underground. I suppose you could probably use schedule 40 above ground too if the location is such that physical contact with the conduit is very unlikely.

Water pipe may not be substituted for electrical conduit.
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#74736 - 04/29/04 06:17 AM Re: PVC Schedule 40 or Schedule 80?
tom07 Offline
Handyman

Registered: 04/19/04
Posts: 693
Loc: Massachusetts
Thanks.

Guess I need some schedule 80.

As for water pipe, there are distributors (e.g. Grainger) who list schedule 40 and schedule 80 pipe, but not conduit, on their web sites -- yet have all the conduit fittings. I suspect they are selling something that is usable for both. Is that possible? Can stuff marked as schedule 40/80 always be used as conduit even if it is listed as pipe? Or are "schedule 40 pipe" and "schedule 40 conduit" two distinct items?

Thanks,

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#74737 - 04/29/04 10:29 AM Re: PVC Schedule 40 or Schedule 80?
monocline Offline
Handyman

Registered: 02/06/03
Posts: 656
The schedule refers to the wall thickness of any type of pipe.
There are many types of pipe, electrical conduit is one.

There are many types of electrical conduit.
Not all pipe is approved for use as electrical conduit.

Bryan

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#74738 - 04/29/04 07:34 PM Re: PVC Schedule 40 or Schedule 80?
3phase Offline
Carpal Tunnel

Registered: 09/09/02
Posts: 6849
Loc: Licensed Electrical Contractor...
Tom, PVC conduit is rated for exposure to sunlight. I don't believe that water pipe is rated for this exposure. In my area we do use the sched 40 above ground, by we I mean the contractors and the POCO. Supply houses in my area do not even carry sched 80 conduit only 90 deg sweeps. The I.D. of the sched 80 is slightly smaller due to the thicker wall.

The short answer is to not use water pipe, it will not pass the inspection by the AHJ.
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#74739 - 04/29/04 08:33 PM Re: PVC Schedule 40 or Schedule 80?
tom07 Offline
Handyman

Registered: 04/19/04
Posts: 693
Loc: Massachusetts
Ah, that's why they say pipe has to be painted -- but not conduit.

Why only 90 degree sweeps as schedule 80? Do they need to be stronger for some reason?

I thought NEC required schedule 80 above ground. Is it more a local thing?

On the smaller ID, what needs to be done to avoid an edge where schedule 80 meets schedule 40? Just file it down?

Thanks,

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#74740 - 04/29/04 08:37 PM Re: PVC Schedule 40 or Schedule 80?
Bob_Fleming Offline
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Registered: 06/28/01
Posts: 28202
Loc: Ft Collins, CO USA
I'm curious about this water pipe vs plastic conduit thing. I would normally use plastic conduit (vs water pipe) for electrical since it comes with a fitting on one end. Convenient!
BUT, white PVC water pipe is used above ground here for sprinklers. I have never heard of it deteriorating in sunlight. While I don't normally use it on the pressure side of sprinkler valves, many people do. So it is not only exposed to sunlight but to house water pressure. You would expect the water to be cool, EXCEPT after it has been stagnant for a few hours in the sunlight.
So I see no reason to think that the white PVC water pipe is in any way inferior to the gray PVC conduit above ground. In fact, for water pressure and sunlight exposure, I would expect the gray conduit to be inferior.
BTW the code here does not allow use of PVC conduit above ground at all! Ok underground, but must be transistioned to rigid steel conduit above ground. The PVC conduit is not considered substantial enough to resist physical damage.

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#74741 - 04/29/04 08:45 PM Re: PVC Schedule 40 or Schedule 80?
3phase Offline
Carpal Tunnel

Registered: 09/09/02
Posts: 6849
Loc: Licensed Electrical Contractor...
Tom, yes the NEC does specify sched 80 above ground but sched 40 can be used if the AHJ will let it, & it may be a regional thing. Sometimes different areas do allow different things.

As to the ridge, it is usually OK and a lot depends on how the wire is being pulled. If you pull towards the bell mouth of the conduit it will not be a problem.
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#74742 - 04/29/04 08:54 PM Re: PVC Schedule 40 or Schedule 80?
3phase Offline
Carpal Tunnel

Registered: 09/09/02
Posts: 6849
Loc: Licensed Electrical Contractor...
Bob, the issue of using water pipe vs conduit comes down to a case of listed or approved uses. The AHJ may define what is approved but the water pipe is not UL listed to use as electric conduit. In my opinion there is also the issue of workmanlike, yes a catch-all phrase, but it does exist in the NEC.

The gray PVC is definitely marked and listed to be sunlight resistant. And it does hold up when exposed to sunlight.

I would agree with the transition to metal when the conduit exits the ground. The metal is no doubt more resistant to damage from a blow.
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