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Old 06-30-2006, 04:40 PM   #1
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Type DZYR/Electrical vs. type QNMJ/Plumbing PVC Pipe


I have been working in electrical construction and design for the past 13 years and have had many occasions to witness the installation of underground PVC pipe, for both concrete encased and direct burial applications. Typically, grey PVC pipe, type “DZYR,” is used for electrical applications whereas white or type “QNMJ” is used for plumbing. Further, type “DZYR,” is manufactured according to UL651 whereas that used for plumbing applications follows ASTM standards.

I had a conversation the other day with a local electrical inspector/AHJ regarding the feasibility of using “plumbing” PVC in lieu of “electrical” PVC piping for a run between my house and detached garage (I had a bunch of extra sticks laying around and considering that it would be carrying some power limited signal/control wiring for alarm, telephone and intercom, I didn’t really think that it was a big deal). He wigged and basically threatened to cut off my legs if I did. Once he calmed down, I asked him what specific characteristics of the “QNMJ” pipe made it unsuitable for use as an electrical conduit and he admitted that he didn’t know (other than “It ain’t grey.”).

I would like to study the appropriate ASTM and UL specifications to understand what makes these two products different but they are not published on line and are very expensive to purchase. I would guess that the plumbing variety would need to withstand higher pressures/temperatures when compared to the electrical type but again, this is only a hunch.

If anyone has any thoughts, please share! And thanx!

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Old 07-01-2006, 07:49 PM   #2
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Type DZYR/Electrical vs. type QNMJ/Plumbing PVC Pipe


Building Codes allow for alternative materials, designs and methods provided the alternate compliance path has been approved.

The International Residential Code, for example, states:

R104.11 (IRC 2003)
Quote:
"The provisions of this code are not intended to prevent the installation of any material or to prohibit any design or method of construction not specifically prescribed by this code, provided that any such alternative has been approved.

An alternative material, design, or method of construction shall be approved where the building official finds that the proposed design is satisfactory and complies with the intent of this code, and the material, method or work offered is, for the purpose intended, at least the equivalent of that presdribed by the code"
The section goes on to state that the building official can require tests or engineering stamps or etc...to show evidence that the method or material can comply.

I do not have an answer for you other than that the precribed codes are not written in stone and alternative methods and materials can be used if the intent of the code is served.

In the case of underground conduit, that intent would be water protection of the cables run inside the conduit as well as physical protection of the cables.

If QNMJ can serve to meet the same intent as DZYR, especially for the limited energized cables you will be running, as a building official (not an electrical inspector) I don't (at least in principal) see the problem.

Electrical codes, however, do insist that materials be 'listed' and 'labled' by 3rd party inspection agencies and approved for the intended purpose. And since AHJs can be held responsible for their decisions regarding life and limb, they are going to be reluctant to grant you approval for an alternative method and material.

Put another way, you'd better have a reason more pressing than "I just have some PVC sticks laying about and would rather use them than spend a few bucks on approved materials" and be ready to back up your alternate method and material claims with things like an electrical engineer's stamped seal on the design if you want approval.

In the end it may be less aggravating and cheaper to just buy and use DZYR.

Mine isn't much of an answer one way or the other, but it at least shows that you likely can get approval to use plumbing pipe if you put enough effort into the process.

And I admit you are doing just that.

One place you can look for support if you haven't already done so, is at the International Codes Council website where you can look up Evaluation Reports of products by manufacturer and type:

http://www.icc-es.org/Evaluation_Reports/index.shtml

Luck


Last edited by manhattan42; 07-01-2006 at 10:54 PM.
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Old 07-01-2006, 09:38 PM   #3
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Type DZYR/Electrical vs. type QNMJ/Plumbing PVC Pipe


doesn't the grey stuff have thicker walls(sched 40), therefore wouldn't match up to the sweeps you need for pulling it?

Also, if it's low voltage, what does it matter what it's in.

The sprinkler guys always use a piece of white pipe for their low voltage between the controller to the ground where it is just direct buried.
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