Radio Location Lead Pipe - Page 1
Forum section: electronics / rf-microwave

author: cosmarchy
author_rank: Contributor
timestamp: July 13, 2020, 07:51:54 pm
content: Bit of a long shot but does anyone know firstly whether it is possible to trace an old lead pipe under cement using radio location and secondly of any ready built schematics to do it?I've a lead water pipe which needs to be replaced and for the most part it goes under a concrete slab. I am to replace it with plastic and as I have no other route than to cut it out, I'd use the hole I make removing the old lead pipe to put in the plastic one.The problem I have is locating the path of the old lead pipe.I saw an interesting article about someone using a wire up a plastic pipe and an AM radio which worked well for a plastic pipe but would not work well for lead, nor do I have access to poke a wire up it, at least for the moment...I wondered whether instead of poking the aerial up the pipe, whether you could use the pipe as the aerial? Could this be done? Has anyone done this?Thanks

author: richnormand
author_rank: Unknown
timestamp: July 13, 2020, 09:39:18 pm
content: I had success locating a copper pipe (1/2") many many years ago about a foot underground between the house and the garage.It was there when we got the house and my parents had no idea on its exact path.Since I had access to both ends I clamped a hefty wire from the garage end, ran overground back to the house with a detour away from where I suspected to pipe to be. Unhooked the house side of the pipe to isolate the run. Hooked up a 50W audio amplifier good for 4 ohm load with a 2 kHz tone signal and carefully ramped up the volume with the pipe as part of the loop. I used a home made 6" diag coil on a wood frame with about 100 to 200 turns as a pick-up coil plugged to the microphone input of my portable tape recorder and got a very usable signal using the generated magnetic field from the pipe.The 2kHz allowed me to discriminate easily from the 60 and 120Hz permeating everything.This link should give you ideas:https://www.radiodetection.com/sites/default/files/Theory-Buried-pipe-manual-V10.pdfI assume my scheme worked well because the soil was dry at the time and above the water table. Also if your concrete has rebar in it that might complicate matters.....Good luck with it..

author: RoGeorge
author_rank: Super Contributor
timestamp: July 13, 2020, 10:02:21 pm
content: Would it be possible to fit the new plastic pipe inside the old lead pipe, so to skip all the digging?

author: CaptDon
author_rank: Super Contributor
timestamp: July 14, 2020, 01:52:27 pm
content: Metal detectors seem to see lead pipes real well.Why re-invent the wheel? Is the pipe to far downto find with a metal detector? If it is that far downthen radio location at best will be an approximation.What a shame Ground Penetrating Radar costs somuch. That would find it.

author: Bud
author_rank: Super Contributor
timestamp: July 14, 2020, 02:28:54 pm
content: If the pipe is only few inches deep down, a thermal camera could be tried. You will need to run cold or hot water through the pipe for a few min to create a temperature gradient which can be detected by the camera. That should work even if the concrete has rebar which may make metal detector not helpful.

author: cosmarchy
author_rank: Contributor
timestamp: July 14, 2020, 05:55:49 pm
content: Many many thanks for your suggestions guys.@bud, unfortunately some very 'kind' people broke in a while back and nicked all the copper attached to the lead pipe and since I have no idea where this pipe goes I cannot guarantee running any water through the pipe wont cause some damage somewhere. So unfortunately this isn't an option although a very good one@CaptDon, I think I'll try this. I don't know why I never thought of this. It sounds logical if you think about it.@RoGeorge, another great suggestion but the lead pipe is about 12mm ID so this is out of the question

author: cdev
author_rank: Super Contributor
timestamp: July 20, 2020, 12:23:03 am
content: I have a cheap signal detection probe/signal tracer that I use for tracing cables through walls. It works great. It can detect a cat 6 cable through a concrete wall up to several feet away. They cost around $20 on ebay. Just clip a wire to the pipe and since the pipe is already grounded (it might be worth saving for that reason, as a ground. use a wire as you suggested for the return.

author: A.Z.
author_rank: Super Contributor
timestamp: July 20, 2020, 11:59:31 am
content: Did you consider the idea of sliding some steel wire inside the pipe and then using a regular metal detector to track its location ?

author: cdev
author_rank: Super Contributor
timestamp: July 20, 2020, 01:45:53 pm
content: 1. Why does the pipe need to be removed physically, can't it simply be removed from the system at its ends and left in place in the ground? (replaced by a copper or other safe pipe)2. If there is electrical continuity from end to end, and there should be, it should be possible to locate it by a signal generator and receiver, maybe even the cheap kind I mentioned.

author: cosmarchy
author_rank: Contributor
timestamp: July 20, 2020, 03:23:50 pm
content: Quote from: cdev on July 20, 2020, 01:45:53 pmThe idea of removing the pipe is because I have to cut in to the concrete above it in order to lay a new plastic pipe. If I have to cut in to to the concrete above it, I might as well cut a channel and remove the old pipe and use the channel it left to put the new pipe in. Otherwise I'll have to cut the concrete and then dig out a new channel for the new pipe. As they are going to the same place it makes sense to re-use.With the signal generator / receiver idea, how does this work if the pipe is grounded already? If I clip the signal on to the pipe it will already be grounded won't it? so where would you put the ground wire?

author: cdev
author_rank: Super Contributor
timestamp: July 20, 2020, 07:56:30 pm
content: If the pipe is embedded in concrete, it may not be that well grounded, also since the pipe is metal its a significantly better conductor than anything that isnt. Basically, I have one of these things and its surprisingly sensitive. I use it quite a bit around the house (admittedly above ground, and nowhere near as dense walls, etc.) but it can consistently pick up a signal from six or ten feet away. And it gets louder the closer you get. I would first try connecting the tracer to it as if it was a normal single conductor, and connecting the tracer transmitter to a known ground as well. That would probably work but if not, then ground the far side of the pipe to a ground there, if available. If not connect it to the ground inside the house by a long wire if need be, but run that wire far enough from where you are with the pipe that it doesnt confuse your receiving the local pipe?Anyway, thats how I would start out doing it. There are a zillion ways to spend money but this method of cable location is popular because it works. And its cheap. These devices are very cheap. Some now combine a basic tester for ethernet cables.As desscribed elsewhere, you could also use a tape head and an audio amp, or something like that. But thats basically the same thing. And you are still going to need some means of exciting the pipe, i.e. an audio oscillator.

author: cosmarchy
author_rank: Contributor
timestamp: July 20, 2020, 09:07:41 pm
content: Ok, thanks for this, it's worth a try.There are loads out there so are there any recommendations so I don't get a complete load of rubbish? I'm sure there are a load of rip-offs and non-functioning ones out there...

author: notsob
author_rank: Frequent Contributor
timestamp: July 20, 2020, 09:11:12 pm
content: There is always the "old" way - hook up one of the spark plug leads from an ICE car motor and trace the "noise" with a cheap AM radio

author: richnormand
author_rank: Unknown
timestamp: July 20, 2020, 09:26:24 pm
content: On a tangent from your original question.You might not have to cut the concrete at all to get a new pipe installed.About 20 years ago the gas company installed a main pipe on the street and delivery to the houses that requested natural gas heating instead of oil.The equipment used allowed for the whole underground installation without breaking any of the sidewalks, street or garage entrances. Only a few small hole at pipe junctions were needed.In my case they burrowed the whole length of the house and only removed the last paver to get the pipe to the house meter.It might be useful to find if this option is available from a contractor in your area and save you a lot of grief and a nasty patch in the concrete...