Rigid metal conduit underground

[bluedog225]

I’ve been reading about using rigid metal conduit underground. I’ve got a run of about 40’. Looks like corrosion is a real issue. The alternative is schedule 80 pvc. Looks like the rigid can be buried at 6” while the PVC requires 18”. Ugh.

And the other alternative is direct burial cable. 24” but could be a pretty narrow trench.

I’m about to abandon my plan to use my nice 2” rigid conduit underground and go with schedule 80. I wanted to check in and make sure this was the right move for maximum service life. I’ll use the rigid somewhere else.

 

[sparky 1971]

Underground rigid is for gas stations. I don't know why anyone would want to subject themselves to that kind of work otherwise.

Use PVC. You can use schedule 40 and save some money. Schedule 80 is for where damage could occur.

And a trencher doesn't know the difference between 6" and 18" of depth.

 

[bluedog225]

My trencher is almost 60. He knows….

 

[Mzungu]

We stopped using rigid metal underground many years ago. Nowadays its Teck cable with special explosion proof glands and seals for gas stations. For all other "normal" UG conduit installs its rigid PVC schedule 40. 18" for non-vehicular traffic areas.

 

[mike93lx]

Underground rigid is for gas stations. I don't know why anyone would want to subject themselves to that kind of work otherwise.

Use PVC. You can use schedule 40 and save some money. Schedule 80 is for where damage could occur.

And a trencher doesn't know the difference between 6" and 18" of depth.

Agree except on the depth. You must not have rocks or clay in your soil.

 

[sparky 1971]

Agree except on the depth. You must not have rocks or clay in your soil.

Oh, there's nothing but clay around me and about 25 miles to the South it turns pretty rocky. The guy I use to trench has a Ditch Witch that will get about 6' of depth. If and when a rock is hit, he turns around and uses the attached back hoe to get it out. It's been 11 years since I trenched. I tell people someone else is doing the digging and that I have a guy, or they can take care of it themselves.

 

[mike93lx]

Oh, there's nothing but clay around me and about 25 miles to the South it turns pretty rocky. The guy I use to trench has a Ditch Witch that will get about 6' of depth. If and when a rock is hit, he turns around and uses the attached back hoe to get it out. It's been 11 years since I trenched. I tell people someone else is doing the digging and that I have a guy, or they can take care of it themselves.

Well, that's cheating. Homeowners rent machines that most certainly do care about the difference between 6" and 24". I have no rocks around me now, but it's hard clay and back in New England, the rocks were absolutely everywhere.

Sounds like that's a good guy to keep on your side

 

[sparky 1971]

Well, that's cheating. Homeowners rent machines that most certainly do care about the difference between 6" and 24". I have no rocks around me now, but it's hard clay and back in New England, the rocks were absolutely everywhere.

Sounds like that's a good guy to keep on your side

The last time I trenched I rented a walk behind trencher. I don't like to say never, but I hope to never, ever use one of those POS's again. If I have to I will get a mini excavator and tear the hell out of everything, but there's no way I'm using a trencher. That's where I give people to option of my guy or figuring it out themselves.

 

[sparky 1971]

My trencher is almost 60. He knows….

By using PVC instead of rigid, the saving will pay for at least part of a machine rental. I would look into a mini excavator. Walk behind trenchers are a PITA. Or you could hire someone that digs for a living and get it over with.

 

[nadogail]

Trench Diggers are usually found standing around in the Home Depot Parking Lot.

 

[Chuckster in NJ]

I had a Ditch Witch 1420 walk behind trencher and most of the time after a use in "tough soils" it had to be repaired……. The machine "earned it’s keep" over the years but it was a 4 hour maintenance job in my shop after 700 feet of trenching.
I purchased the trencher in 1984 and sold it in 1999, I had no problem selling the machine because it would fit through a 36” gate and was well maintained.

 

[dogdog]

dependents on what you are doing and what is important to you... GRC/RMC are better at preventing damages from some one digging into it...but more expensive... and is NPS threads I think. It is heavily galvanized or zinc coated to prevent rust... don't think the ones I bury from 2013 is rusting yet at all. PVC is cheaper, pretty sure you know the rest. I dig my trench down to 30"... it's not that hard to dig 40' . didn't even hire any home depot park lot rental special.

 

[billconner]

I have twice used rigid metal because of the shallow depth - one or two sticks of 1". I see 2" rigid is $108 a stick vs 2" PVC at $35. 1" $44 vs $15. Digging by hand for a 10 to 15' run, the rigid metal seemed worth it to me. Going 40 ft with 2" - $432 vs $140 in material - I'd never hand dig for 18" cover, might for 6".

 

[Jim greengo]

Underground rigid is for gas stations. I don't know why anyone would want to subject themselves to that kind of work otherwise.

Use PVC. You can use schedule 40 and save some money. Schedule 80 is for where damage could occur.

And a trencher doesn't know the difference between 6" and 18" of depth.

I've used it underground in industrial settings,but it's been many years ago.

 

[Jim greengo]

And I dont miss bending rigid conduit,ran more than I'd like to remember in ag processing plants in the 90s.
I'll take bending a mile of 1" emt over 100' of freaking rigid and threading that **** together/hanging it! Hahaha

 

[sparky 1971]

And I dont miss bending rigid conduit,ran more than I'd like to remember in ag processing plants in the 90s.
I'll take bending a mile of 1" emt over 100' of freaking rigid and threading that **** together/hanging it! Hahaha

I hate rigid. I have a 300 threader and dies up to 2", a Greenlee 1818 with shoes to 1-1/2 and a segment bender with shoes that are way bigger than I ever am going to deal with. If I never have to use any of those again I won't complain one bit. My idea of rigid these days is a mast that goes straight up.

 

[beemerphile]

Oh, there's nothing but clay around me and about 25 miles to the South it turns pretty rocky. The guy I use to trench has a Ditch Witch that will get about 6' of depth. If and when a rock is hit, he turns around and uses the attached back hoe to get it out. It's been 11 years since I trenched. I tell people someone else is doing the digging and that I have a guy, or they can take care of it themselves.

It's all about location. I had a guy digging what I thought was going to be a 24" direct burial trench for the feeder to my new house. The DW hit rock and every time one of the carbide teeth impacted the rock I could feel it under my feet 30 feet away because I was standing on the same rock he was banging on. Forget the backhoe. I finally carved out about 9 inches of cover but ended up running the feeder in metal conduit on the side of my shop to get past the mega rock.

 

[Jim greengo]

I hate rigid. I have a 300 threader and dies up to 2", a Greenlee 1818 with shoes to 1-1/2 and a segment bender with shoes that are way bigger than I ever am going to deal with. If I never have to use any of those again I won't complain one bit. My idea of rigid these days is a mast that goes straight up.

Amen brother! Hahaha

 

[wyliesdiesels]

If you must use rigid, I would wrap it with 10mil pipe wrap tape...

 

[walrus]

If you are going to wrap pipe might as well hook an anode on it also. Rigid will outlast the OP if his comment on ditch digger being 60 is true. What might stop him from using rigid is price

 

[Bert_]

You guys complaining about rigid...

 

[sparky 1971]

You guys complaining about rigid...

That reminds me of the one and only big rigid job I ever worked, a grain elevator remodel. It was supposed to take a month, but drug on for five and I hated every minute of it. The largest conduit we used was 2" but during January and February it was so cold that in between threads we had to put the oil in a shed with a heat lamp shining on it. Otherwise the oil wouldn't pump. Never again.

 

[roc_on_the_rocks]

Trench Diggers are usually found standing around in the Home Depot Parking Lot.

They aren't seen in the midwest though, but I know it's a common thing in California.

 

[Jim greengo]

That reminds me of the one and only big rigid job I ever worked, a grain elevator remodel. It was supposed to take a month, but drug on for five and I hated every minute of it. The largest conduit we used was 2" but during January and February it was so cold that in between threads we had to put the oil in a shed with a heat lamp shining on it. Otherwise the oil wouldn't pump. Never again.

We did a soybean oil processing plant in south dakota in mid 90s.
Ran miles of rigid pipe on that job,lots of 3" and 4" stuff between buildings.
Used to wire lots of packing plants back in the day also,anything that was anywhere near live cattle was rigid.
We ran emt for most stuff on the fab side and freezers though.
That's a much younger man's sport to say the least,I'd rather flip hamburgers at mcdonalds than do that stuff anymore!

 

[Norcal]

It seems that the worst corrosion w/ metal underground pipe is where it emerges from the ground, so I just use pipe wrap tape there.

 

[Bert_]

That reminds me of the one and only big rigid job I ever worked, a grain elevator remodel. It was supposed to take a month, but drug on for five and I hated every minute of it. The largest conduit we used was 2" but during January and February it was so cold that in between threads we had to put the oil in a shed with a heat lamp shining on it. Otherwise the oil wouldn't pump. Never again.

I actually said no to this job the first time. But they came back a couple days later and asked again so I could pretty much set my own terms. We had snow but the temp was probably 25* so not bad really. Ran a 600A feeder to a dryer. Just a few day job. Snow is all melted now.