Finding/Locating sewer line under basement floor

I own a property that has a cast iron sewer line that runs under the basement floor, and I want to be able to mark out and locate where it runs under the basement floor. I know that I could hire a company to come out and do that, but I am wondering if there are any fairly cheap, creative, and interesting/fun ways for me to try to locate the line myself.
For example, is there some kind of small signal generator that I could attach to a sewer line snake and detect the signal from above with some type of detector? -- maybe something that Radio Shack or some electronics store might sell?
Or, are there relatively inexpensive underground pipe-locating devices that I could rent somewhere and do the job?
Would a metal detector be able to detect a cast iron pipe under a concrete floor (assuming that the pipe is not down very far below the floor?
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Limp Arbor wrote:

I heard where one dowser tried to investigate a crop circle and his head exploded.
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On 1/11/2012 4:22 PM, HeyBub wrote:

Sniper with a .50 caliber Barrett M107 at least a mile away.
TDD
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The Daring Dufas wrote:

Oooh! Didn't think of that! It has much to commend it.
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On 1/12/2012 5:36 AM, HeyBub wrote:

Sorry, I was fantasizing again. ^_^
TDD
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Joe wrote:

Thanks, but I am not sure how a "magnetic compass" would work.

I am also not sure where I would rent whatever a regular plumbers device is.

That may work. I wonder if anyone here has ever tried that since I have no experience with using any metal detectors. Maybe I'll try searching to see if the are metal detector websites and/or forums where I can get more info on how well a metal detector may work for this.
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Metal Detector? White out of Washington
Stay away from 'toys'
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the underground line is likely terracota pipe. it may not be metal once it goes underground
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A metal snake should show up with a metal detector, use steel not stainless. I tried to see if my pipe bends anywhere by using a camera. After a lot of fooling around, I gave up looking at the whole pipe. I had problems with my feed method and camera position. Saw hairs, webs, a worm, and a creapy crawler. I was also looking for roots, but didn't see any as far as I got.
Greg
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I just gave myself an idea. Got to borrow the metal detector!!
Greg
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You might try an electronic stud finder at the sensitive setting, it depends on how deep the pipe is buried under the concrete. Worth trying.
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On 1/11/2012 6:51 PM, hr(bob) snipped-for-privacy@att.net wrote:

A small RF transmitter attached to a fish tape could work. I've used small pocket AM/FM radios set on AM to find live wires in walls before. A small AM transmitter that put out a warbling signal could be used. Might be a fun little project? ^_^
TDD
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I had a problem with my sewer line where the line had to be located under a concrete garage floor. A plumber used a piece of wood placed between his ear and floor to help amplify the sound. He then had his partner tap in various places on the floor and also run some water down a drain. Apparently, between those two tests, he was able to locate the pipe confidently but not perfectly. He also ran a snake down a clearout and measured how much was being fed as well as detecting any noise. I suspect you can use a stethoscope instead of a piece of wood.
Good Luck.
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On Wednesday, January 11, 2012 1:04:38 PM UTC-5, Ron wrote:

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Yes there are. Go down to your local tool hire shop.
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On 7/15/2013 12:16 PM, harryagain wrote:

If it's not too deep, a metal detector.
The pipe locator guys inject a signal on the pipe and detect it from above.
I built a crude one. used a function generator at 6.5kHz to inject a signal between the pipe and ground. That just happened to be the peak sensitivity of the receiver.
Sensed it with a coil wound on a vertical ferrite stick. Plugged that into the microphone input of a computer. Used a sound card scope to detect it. I used a pda and a spectrum analysis program, but any old computer should work.
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