RMC question in DG in SoCA

Jarnipman

Member
Location
Minnesota
So I'm doing a job - it was supposed to be super easy. Part of it is to trench 75 feet and then i kick some PVC into the trench and I'm done with it - super easy until the trencher bounced off solid bedrock at less than a foot and there is no option of getting a rock grinder in there to cut the granite, nor would I want to do such a thing. So annoying, who put the bedrock there!!! So my only option is RMC to go underground to meet the minimum cover requirement without concrete. On top of the bedrock is decomposed granite that is so porous looking that as far as I can tell I may as well be installing the RMC in a swimming pool. Customer asked me how long will the RMC l last in Southern CA desert climate DG if it's wet - it's under a lawn that is also a drainage plane so it's going to be wet? I have no idea how long it will last in this climate and I hate RMC in wet environments because I despise anything that corrodes and at some it will leak and basically the THHN will be underwater in that pipe right? Anyone know how long the RMC will last in wet So CA DG?
 

Jarnipman

Member
Location
Minnesota
Note 5 says I can install PVC on top of the granite with 2" of concrete poured on top - so basically as shallow as the granite is. Yeah I guess I have a choice of doing RMC or pouring in 7 bags of concrete and hauling away a few hundreds pounds of fill dirt.
 

Jarnipman

Member
Location
Minnesota
Yeah, dry concrete rules for little things like this 2" trench cover - I tried that for fence posts as well and it took me a while to convince myself that it works, but totally does. I guess I can pour the concrete, but going back to my original question how long does RMC last in desert CA DG? I'm genuinly curious...I am 100% non-metallic underground, but there are times where it is enticing when a trencher won't fit to dig. I remember as a kid always digging up and replacing galvanized water pipe for side jobs and since then I have an aversion to anything metal underground. I won't install it because I don't feel like I can gaurentee it, but maybe I am giving RMC a bad rap?
 

zooby

Member
Location
Indiana
Occupation
maint. electrician
Yeah, dry concrete rules for little things like this 2" trench cover - I tried that for fence posts as well and it took me a while to convince myself that it works, but totally does. I guess I can pour the concrete, but going back to my original question how long does RMC last in desert CA DG? I'm genuinly curious...I am 100% non-metallic underground, but there are times where it is enticing when a trencher won't fit to dig. I remember as a kid always digging up and replacing galvanized water pipe for side jobs and since then I have an aversion to anything metal underground. I won't install it because I don't feel like I can gaurentee it, but maybe I am giving RMC a bad rap?
i dont know about the "desert" but there is ocal (pvc coated)thats been in the ground 33-34 years at this indiana facility. probably cheaper to pour concrete over yours though.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
Yeah, dry concrete rules for little things like this 2" trench cover - I tried that for fence posts as well and it took me a while to convince myself that it works, but totally does. I guess I can pour the concrete, but going back to my original question how long does RMC last in desert CA DG? I'm genuinly curious...I am 100% non-metallic underground, but there are times where it is enticing when a trencher won't fit to dig. I remember as a kid always digging up and replacing galvanized water pipe for side jobs and since then I have an aversion to anything metal underground. I won't install it because I don't feel like I can gaurentee it, but maybe I am giving RMC a bad rap?
What is "DG"?
 

mtnelect

HVAC & Electrical Contractor
Location
Southern California
Occupation
Contractor, C10 & C20 - Semi Retired
Yes, boulder is a key word in the City of La Crescenta, California. You can drive down any street and find boulders used for landscaping, too large to remove.
 

jdrive

Member
Location
Chicago
Occupation
Electrician
We use RMC underground in the Chicago area all the time. Not exactly the same climate but some of the soil areas are very moist. Have seen several installs that are 40-50yrs old and still in decent condition (surface rust, but still intact pipe walls). When we run underground we use XHHW-2 instead of THWN as the insulation is a bit thicker and more durable.
 
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