I can't find any standard for the installation of u/g conduit. I have a special condition where the conduit is in a trench on a new construction site and the sewer trench has been dug, crossing the electrical trench. Leach rock has been put in the sewer trench and covers the exposed conduit. Are there any specifications that handle this condition?
u/g conduit
- Thread starter raywward
- Start date
- Status
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: u/g conduit
Not in the NEC. The NEC covers cover depth, type of conduit, bends etc. See Chapter 300.
Not in the NEC. The NEC covers cover depth, type of conduit, bends etc. See Chapter 300.
G
Guest
Guest
Re: u/g conduit
Typically it would be part of the drain field of a septic tank system. The leach rock would allow the processed effluent from the septic tank to leach into the adjacent soil. This means the conduit will be in grey water. Or, technically it may be black water. In my area they use river rock for leach (drain) rock. Some places use crushed rock, but that varies by school-of-thought (engineer's option). Sometimes it's 1-1/2" drain rock and sometimes it's smaller-- again engineer's option.
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
Re: u/g conduit
What is the conduit for- service, branch circuit? What is it- RNC?
Is the "sewer" pipe part of a septic field? That would explain the leach rock (crushed stone).
Assuming (and hopefully) it's RNC there is nothing in the NEC that would cover this situation other than protection from physical damage. Kind of like crossing a stream.
I would maintain adequate cover, keeping it well below the crushed stone. I suppose you could pour concrete for a distance either side of the crossing.
What is the conduit for- service, branch circuit? What is it- RNC?
Is the "sewer" pipe part of a septic field? That would explain the leach rock (crushed stone).
Assuming (and hopefully) it's RNC there is nothing in the NEC that would cover this situation other than protection from physical damage. Kind of like crossing a stream.
I would maintain adequate cover, keeping it well below the crushed stone. I suppose you could pour concrete for a distance either side of the crossing.
Re: u/g conduit
The only thing the NEC would say would be that the conduit used would be "suitable for the purpose". I would think that in a leaching field would be corrosive, therefore PVC conduit would be my choice, but it would also need to be protected from abuse, so the best choice would be PVC coated rigid galvanized conduit for the portion of the UG run that crosses the leaching field.
Earl
The only thing the NEC would say would be that the conduit used would be "suitable for the purpose". I would think that in a leaching field would be corrosive, therefore PVC conduit would be my choice, but it would also need to be protected from abuse, so the best choice would be PVC coated rigid galvanized conduit for the portion of the UG run that crosses the leaching field.
Earl
pierre
Senior Member
- Location
- Westchester County, New York
Re: u/g conduit
The NEC also covers corrosive conditions. This may fall under the corrosive condition and not be permitted. This is one of the few times I would say 90.4 comes into play and the AHJ has to determine if it is safe.
Pierre
The NEC also covers corrosive conditions. This may fall under the corrosive condition and not be permitted. This is one of the few times I would say 90.4 comes into play and the AHJ has to determine if it is safe.
Pierre
Re: u/g conduit
Ido a lot of septic systems here. is taht what we are talking about? If so we are not allowed to be crossing the disposal feild at all in our area. If you are simply in or crossing the trench of the solid waste line there should be no problem using any of our allowed conduits. Personally I would only use PVC in this situation because of the obvious reason that it will never ROT out.
Ido a lot of septic systems here. is taht what we are talking about? If so we are not allowed to be crossing the disposal feild at all in our area. If you are simply in or crossing the trench of the solid waste line there should be no problem using any of our allowed conduits. Personally I would only use PVC in this situation because of the obvious reason that it will never ROT out.
joe tedesco
Senior Member
- Location
- Boston, Massachusetts
Re: u/g conduit
cselectric
Senior Member
- Location
- Wisconsin
Re: u/g conduit
I don't see an NEC issue here (except for, possibly, 300.5(f) as Joe T. stated.) However, I would highly recommend you sit down with the septic designer on the job and/or talk with the city inspector that handles septic field installations. You may very well be in violation of a building code other than the NEC here.
I don't see an NEC issue here (except for, possibly, 300.5(f) as Joe T. stated.) However, I would highly recommend you sit down with the septic designer on the job and/or talk with the city inspector that handles septic field installations. You may very well be in violation of a building code other than the NEC here.
ceb
Senior Member
- Location
- raeford,nc
Re: u/g conduit
I am going to throw my $.02 in. I have seen a code on this but I cannot put my hands on it. one thing it said was you could run elect. in the same ditch with water but the elect had to be 12" above water line. at 18" for the elect the water would need to be 30" with the 12" earth on top then the elect.to comply with the 18" rule.
I am going to throw my $.02 in. I have seen a code on this but I cannot put my hands on it. one thing it said was you could run elect. in the same ditch with water but the elect had to be 12" above water line. at 18" for the elect the water would need to be 30" with the 12" earth on top then the elect.to comply with the 18" rule.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: u/g conduit
More important than the conduit used it the conductor. Remember all conduit leaks, it not designed to be water tight. THHN/W although wet location rated, will not hold up long in an corrosive enviroment. I would use XHHW, PVC condcuit, if you are concerned about it being dug up, encase it in concrete. You could put a handhole at one end and pitch the ug conduit to it to allow the ug conduit to drain.
More important than the conduit used it the conductor. Remember all conduit leaks, it not designed to be water tight. THHN/W although wet location rated, will not hold up long in an corrosive enviroment. I would use XHHW, PVC condcuit, if you are concerned about it being dug up, encase it in concrete. You could put a handhole at one end and pitch the ug conduit to it to allow the ug conduit to drain.
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