Schedule 40 vs. Schedule 80 PVC conduit underground 6

[bdn2004]

I'm upgrading the service to my house. I intend to put it in underground. The Utility requires schedule 80 PVC pipe that is exposed near the meter base and at the service pole.

There is about a 75 feet from the pole to the house where the new service entrance will run. The Utility told me to run a conduit underground. This section where I intend to put it screams for some landscaping that either I or the next owner will surely put in. I can see rototillers, spade shovels, etc directly over this conduit and cable.

I just wonder for safety's sake would it be better to install Schedule 80 the whole way, encase schedule 40 in concrete, and if I did encase it, or dig it down deeper...is schedule 40 good enough?

 

[BigInch]

Can't argue about the cost not being prohibitive. Besides, if you lay the conduit, they can come and install it with a quick pull anytime they want. No waiting around, no lost time. Plastic conduit might offer some protection from hand tools, but its value as protection is indeed minimal when it comes to excavation equipment. You should see what it does to steel pipe. We put red concrete slop or red tablets over our fiberoptic cables paralleling our pipelines, which is the reason I asked.

Turbinegen, Water should be assumed to get into anything placed underground. In fact I've hardly ever seen a conduit that wasn't full of water, or had evidence of it, even in Saudi Arabia. Its only a matter of time. That's why the NEC requires UG ratings for cables placed in underground conduit, if I'm not mistaken. Water DOES get into plumbing systems quite often, as they do not normally run "pressurized" (they're usually designed for open channel flow; atmospheric pressure everywhere only, thus are always sloped) and at times groundwater even infiltrates into potable water supply pipes through lose joints or cracks in the pipe. One of the reasons that septic tanks must be placed away and lower than the nearest water supply piping. They do run pressurized sometimes, most notably after a heavy rain when you see water blowing off the manhole covers, but otherwise, no. However at the same time, when soil water tables are also high, outside hydrostatic pressure can exceed inside pressure even of potable water piping and enter into the pipes, as you correctly note.

As a matter of practice, I wouldn't drill holes in conduit, but rather leave a drain point at the last pull box before connection into a building. Water will get in there one way or another, so it only makes sense to let it get out. A small hole somewhere won't let out enough of it to make any difference anyway.

**********************
"Being GREEN isn't easy" ..Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.live.com/

 

[BigInch]

OK, sorry I interrupted. I'll let you sparkies get back to pushing those electrons around, or is it the holes that you're pushing.

**********************
"Being GREEN isn't easy" ..Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.live.com/

 

[jghrist]

As a matter of practice, I wouldn't drill holes in conduit, but rather leave a drain point at the last pull box before connection into a building. Water will get in there one way or another, so it only makes sense to let it get out. A small hole somewhere won't let out enough of it to make any difference anyway.

What if there are no pull boxes? I wouldn't expect a pull box in a secondary service run from the pole to the house. An overhead service will use a weatherhead to prevent rain from getting into the service, but utilities would not normally put a weatherhead at a service pole.

NEC 250.53 requires raceways enclosing service-entrance conductors to be arranged to drain.

The idea of the drain hole is not to drain all of the water out of the conduit, but to prevent water from getting high enough to get into the house.

 

[BigInch]

Not my problem if there's no pull boxes. I'm just saying a drain hole in the bottom of a conduit ... underground ... won't drain enough water out to stop anything. Mud is a very efficient hole-plugger. In fact a hole in a conduit is just as, if not more, likely to let water in it.

**********************
"Being GREEN isn't easy" ..Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.live.com/

 

[jghrist]

Not my problem if there's no pull boxes. I'm just saying a drain hole in the bottom of a conduit ... underground ... won't drain enough water out to stop anything. Mud is a very efficient hole-plugger. In fact a hole in a conduit is just as, if not more, likely to let water in it.

Put some #2 coarse aggregate around the conduit where the drain hole is. Again, the idea is not to keep water out of the conduit. It is to keep water out of the house. You just need to keep the head lower than the level of the house. You only need to drain the water at a rate that might get into the top of the pole riser during rain.

 

[whammett]

Drilling a weep hole in the bottom of conduit is not the best idea. Biginch is right, water is just as likely to come in if the ground becomes saturated as it is to drain out. You'd do better installing a shroud above the areas of conduit most likely to be compromised (above grade), but thats some SERIOUS overkill.

"Scientists dream about doing great things. Engineers do them." -James Michener

 

[stevenal]

Gotta go with jghrist on this. The back and forth movement of water through the drain hole is not a problem, the point is to keep the water from entering the house.

 

[BigInch]

Any lose soil around the gravel will just move in with the water through the spaces around the rocks. Happens all the time. The gravel fills with muck. You need to at least wrap the conduit and gravel with geotextile to have a chance to keep the soil out of the gravel and conduit, but it still lets the water in. Or out? maybe, but probably not. But do seal it, in any case, at the building penetration.

**********************
"Being GREEN isn't easy" ..Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.live.com/

 

[Electic]

The idea of a weep hole, or vault (manhole) to drain water from a conduit system, is to relieve hydrostatic pressure that could develop in a large system with changes in grade.

Yes a weep hole could conceivably let water in, however that is why you should put this at a low point in the system and hopefully have the service entrance into the building at a higher elevation. Some of this stuff is too basic for engineers, yes?

 

[BigInch]

Its not that complicated. Weep holes are for condensation. If you use them for drainage, just be prepared for them to not work like you think they will.

**********************
"Being GREEN isn't easy" ..Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.live.com/