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#181479 - 10/11/08 08:31 AM Finding underground conduit?
sparkync Offline
Member

Registered: 10/17/02
Posts: 811
Loc: NC
I have a job I am trying to get a run of wire through an existing underground 3/4" conduit. There are wires already in the conduit. I tried to get a fish tape through it but it is stopping underground somewhere. I tried to pull on one of the existing wires to use it as a "pull wire" but they don't budge. I tried to go to the other end and "hook" my other fish tape, and now that fish tape is stuck. I don't want to pull too hard in risk of damaging the existing wires in the conduit. I'll probably cut my fish tape and leave it in there:( I knew I was risking getting it stuck, but had no other alternative at the time. The house is probably 70 + years old and I don't know when the wiring was done. It is in a historical district, and in it's time, was a mansion. Still it's a very nice house with a very large yard.
The pipe terminates outside in a 6x6x4 junction box underground, flush with the grass. There is another empty 3/4" conduit leaving the j box, seemingly going in the same direction I want to go. I pushed a 100 ft. fish tape in it and could feel where it might be going through a 90, but cannot locate it anywhere. I've looked under the house, in the yard etc. Can anyone think of a idea I could use to locate this pipe? The original one goes under an asphalt driveway, and I'm assuming this one does too, since it is headed in that direction and is only about 6 ft. from the edge of the driveway, and I feel no resistance when pushing the fish tape, until I reach the end of the fish tape( 95 ft. in the ground). Digging is sort of out of the question, since there are scrubs lining the length of her house where the conduit may be headed. ( by the way, this is where the "troublesome" conduit is coming out too). If I could find this conduit, I possibly could use it for my homeruns back to the panel. I've thought about maybe getting a helper to see if he could here the fish tape, while I twisted it and moved it around. Anybody got any other suggestions maybe? This is to be a "high tech" job for a "high end" customer, and I've just started. I did caution the customer that there might be problems if I could not get the wire through the conduit, before she signed the contract, but I was hoping for it to go easy:(
I guess my "gut" feeling was right. Any suggestions would be greatly appreciated. I have to go back Monday or Tuesday to try again. Thanks for the input.. Steve...

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#181480 - 10/11/08 09:08 AM Re: Finding underground conduit? [Re: sparkync]
leland Offline
Member

Registered: 08/20/07
Posts: 856
Loc: Lowell area, Ma. USA
Empty conduit? The helper is not a bad idea. I have also used my variable spd drill to spin/flip the snake before with a tywrap on the trigger.

Metal conduit? Use a tone generator with a 9V battery.

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#181497 - 10/12/08 11:15 AM Re: Finding underground conduit? [Re: leland]
homer Offline
Member

Registered: 09/30/04
Posts: 68
Loc: Vancouver, WA, USA
Sparkync,
You can rent locating equipment from some rental stores or hire a locater (probably a better idea) to come to the job site. Since you now have a fishtape in the conduit, connect the transmitter to the fishtape or place the inductive probe around the fishtape and you should be able to easily find the route of the conduit and mark the ground with upside down paint can. Compared to digging up the shrubbery and all that, locate services are very cheap, and also make you look like a professional looking out for the best interests of your client.

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#181498 - 10/12/08 06:12 PM Re: Finding underground conduit? [Re: homer]
twh Offline
Member

Registered: 03/11/04
Posts: 898
Loc: Regina, Sask.
I watched a backhoe operator witch an empty pvc with two 3 foot stainless welding rods. I like a little more technology so I prefer an air compressor.

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#181499 - 10/12/08 06:40 PM Re: Finding underground conduit? [Re: twh]
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
Whenever the topic of tracing conduits comes up, someone is sure to chime in with stories about 'witching.'

To test these theories, the folks at the Sceptical Enquirer actually arranged a test ... pipes and cables of various material, crossing a parking lot that was under construction. Each was marked at the start, and the lot backfilled and graded. Then, various "witchers" were asked to trace the runs.

Despite considerable effort, SE was not able to find any who could trace even one. Several of the :experts" asserted that the trial was, in some way, unfair. It seems the method only works at places other than test sites, and only when no one is watching.

Not that there is not any value in being able to 'read' the surroundings. Sometimes ground contours, building layouts, and other features can give you valuable clues as to where the pipes have been run.

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#181504 - 10/13/08 06:47 AM Re: Finding underground conduit? [Re: renosteinke]
Zapped Offline
Member

Registered: 10/01/02
Posts: 481
Loc: Huntington Beach, CA, USA
I'm assuming that the 3/4 is rigid metallic. Sounds like a collapsed pipe maybe? This is pretty common here in southern cali, especially near the ocean where soil is extremely corrosive.

You could use an inexpensive in-ground tracer tied to one of the existing wires. I have one I picked up for about $180 and I've had very good luck with it, granted the conduit is not too deep. Otherwise, I agree with homer - get a locator service and avoid all the headaches and wasted labor hours.

Good Luck!

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#181505 - 10/13/08 07:30 AM Re: Finding underground conduit? [Re: twh]
walrus Offline
Member

Registered: 07/25/02
Posts: 671
Loc: Bangor Me. USA
 Originally Posted By: twh
I watched a backhoe operator witch an empty pvc with two 3 foot stainless welding rods. I like a little more technology so I prefer an air compressor.

Generally backhoes and excavators are good at finding pipes \:\) usually when your not looking

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#181509 - 10/13/08 03:24 PM Re: Finding underground conduit? [Re: walrus]
sparkync Offline
Member

Registered: 10/17/02
Posts: 811
Loc: NC
I don't guess I explained it quiet well enough. The pipe I'm trying to find is an empty 3/4" pvc run. The other pipe that has the wires from the panel,is rigid when it goes into the ground from the house, but pvc when it comes into the 6x6x4 "j" box in the yard. It goes under an asphalt driveway from the house, and this is about where my fish tape stops. I figure the pipe is corroded into. The wires in the pipe won't even budge.
The pipe I'm trying to locate is empty and comes back out of the 6x6x4 j box in the yard, and heads back in the direction of the house or garage,(it seems). That is the reason I'm trying to find where it goes, to see if I can tap into it (if it comes out on the other side of the driveway) then go under the house where I can take it back to the panel or "j" box under the house. I found out I can rent something like a metal detector that will trace my fish tape when I push it through. It cost $75.00 a day.I may have to go this route. I have one other option that may work. There is already a circuit in the j box that goes to an automatic gate, and a switch leg that goes to a post lamp down at their little bridge over their creek. I can get my hot feed from there, and use the switch leg for the lights I am going to install. The lights will pull approximately 9 amps (possibly- (3) 250wt. HPS floods, (1) 150 wt. HPS flood, and (1)100wt. HPS.) My only concern is when the gate shuts or possibly opens when the lights are on, it might create an overload and trip the breaker.
Hope this explains it better. Thanks... Steve

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#181513 - 10/13/08 07:10 PM Re: Finding underground conduit? [Re: sparkync]
EV607797 Offline
Member

Registered: 10/25/06
Posts: 756
Loc: Fredericksburg, VA, USA
Steve:

Would it be possible to try compressed air on the empty conduit? I know that it's a stretch, but the air may either make enough mess or create enough noise to where you can find the other end.

I encountered a similar situation to yours several years ago, but it was about a 300' run of 1-1/2" RMC, about 50 years old. It had a telephone cable in it that we needed to pull out and replace, but it wouldn't budge. No fish tapes, no blowers, no nothing would work so we figured it was a collapsed/rusted-out conduit. We knew that the old cable had to be replaced, hook or crook, so at this point I was more interested in seeing the snake make it through than saving the existing cable.

Due to the property, also similar to what you've described, excavation really wasn't an option. I went for broke and hired Roto-Rooter to come out and give it a try. He was able to run a snake through with a slow spin on it. He obviously knew what he was doing. It turned out to be lots of rust and dirt that the snake managed to loosen enough to not only get the snake completely through, but to dislodge the old cable so we could pull it out. Oh, and by the way, he ran the snake without any kind of cutter head on it; just the raw end of the snake.

I know that in your case, this might not be an option, but I thought I'd throw out another possible solution just in case you run out of ideas.
_________________________
---Ed---

"But the guy at Home Depot said it would work."

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#181514 - 10/13/08 07:11 PM Re: Finding underground conduit? [Re: sparkync]
EV607797 Offline
Member

Registered: 10/25/06
Posts: 756
Loc: Fredericksburg, VA, USA
Steve:

Would it be possible to try compressed air on the empty conduit? I know that it's a stretch, but the air may either make enough mess or create enough noise to where you can find the other end.

I encountered a similar situation to yours several years ago, but it was about a 300' run of 1-1/2" RMC, about 50 years old. It had a telephone cable in it that we needed to pull out and replace, but it wouldn't budge. No fish tapes, no blowers, no nothing would work so we figured it was a collapsed/rusted-out conduit. We knew that the old cable had to be replaced, hook or crook, so at this point I was more interested in seeing the snake make it through than saving the existing cable.

Due to the property, also similar to what you've described, excavation really wasn't an option. I went for broke and hired Roto-Rooter to come out and give it a try. He was able to run a snake through with a slow spin on it. He obviously knew what he was doing. It turned out to be lots of rust and dirt that the snake managed to loosen enough to not only get the snake completely through, but to dislodge the old cable so we could pull it out. Oh, and by the way, he ran the snake without any kind of cutter head on it; just the raw end of the snake.

I know that in your case, this might not be an option, but I thought I'd throw out another possible solution just in case you run out of ideas.
_________________________
---Ed---

"But the guy at Home Depot said it would work."

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