Cheap ways of detecting a PVC pipe underground ?

[Haenk]

An easy way is to use some steel rod and poke into the ground, the tubing will make a "boing" sound (that's how I found some tubing in my garden).
Or use an radio emitter with a long cable, push that into the tubing (maybe taped to a water hose) and a radio. I have used something similar (though ready-made) to find cable defects in the lawnmower signal wire.
I also like the idea of using a declog tool for a power washer. I have one, but did not use it yet (it was very cheap).

[Zenith]

You must have access to one end. What about the other end? Does it go to a drain or soak away, or does it just disappear? It could easily be blocked with tree roots. If you could push a rod through, where would the material clogging it go?

Do you suppose it runs in a straight line, or are there bends? Anything but gentle bends will make pushing anything through far harder, and will make it more likely that debris will be caught and build up. The requirement is not to find where it goes, so much as to clear it.

If you want to trace it using RF, the first problem is to have the conductor/antenna going through it. The commercial systems for doing that have a reel of semi-rigid cable, which seems like a carefully selected material. 

I'd be inclined to hire/borrow a set of drain rods and try those. There are more sophisticated drain clearing tools with rotating heads, that cut up tree roots etc. Breaking up the material clogging the pipe is only part of the problem. Unless it's removed it will soon cause the problem to repeat.

As for dowsing, the time I tried it I was over a water supply to a major city, which was three 3 metre pipes. I didn't notice anything. Maybe I wasn't doing it right, or just don't have that particular ability. I don't have much confidence in it.

[golden_labels]

I find themadhippy’s idea the most reasonable. But, if not: is your location silent? 30–50 cm of ground should pass sound, in particular in low frequency range. If you can shove a small speaker and play loud drum/knocking sound from it, perhaps you could get the rough location of the pipe? Ears should work well enough the a detector. The low frequency used will not let you get the precise position, but I assume you want to dig a hole big enough to have convenient access to the pipe. Which should be enough to hit the pipe.

Dowsing is more religion than engineering, so I'm astonished people in this forum suggest it as a solution. I'm sure there are more appropriate forums for nonsense and quackery.

This probably warrants its own thread, but some ancient religions losing in popularity shouldn’t be taken as a sign of human brain changing. Evolution of complex organisms doesn’t work that quick. It’s the same organ it has been when the solar deities rode their charriots on the sky and Perun was casting lightnings. And in many ways only slightly different than when you’d smack another ape with a stick.

As for dowsing, the time I tried it I was over a water supply to a major city, which was three 3 metre pipes. I didn't notice anything. Maybe I wasn't doing it right, or just don't have that particular ability. I don't have much confidence in it.

But if you was that 1 in 100 people, who found a pipe, you’d never be convinced it was nothing more than a fluke.

[Zero999]

I found a dowsing meter from a home owner too that worked in utilities. Same story, that it works.

I like the salt water idea

If it works, then it would go off all the time, since the human operator is mostly made of water.

Just because a company used it, it doesn't mean it works. Many armies and security agencies used the ADE 651, until it was discovered to be ineffective.
https://en.wikipedia.org/wiki/ADE_651

[Zenith]

As for dowsing, the time I tried it I was over a water supply to a major city, which was three 3 metre pipes. I didn't notice anything. Maybe I wasn't doing it right, or just don't have that particular ability. I don't have much confidence in it.

But if you was that 1 in 100 people, who found a pipe, you’d never be convinced it was nothing more than a fluke.

I'd be convinced if I, or someone else, could consistently find pipes or underground streams, with success significantly greater than chance.

[tigrou]

You must have access to one end. What about the other end? Does it go to a drain or soak away, or does it just disappear? It could easily be blocked with tree roots. If you could push a rod through, where would the material clogging it go?

Do you suppose it runs in a straight line, or are there bends? Anything but gentle bends will make pushing anything through far harder, and will make it more likely that debris will be caught and build up. The requirement is not to find where it goes, so much as to clear it.

If you want to trace it using RF, the first problem is to have the conductor/antenna going through it. The commercial systems for doing that have a reel of semi-rigid cable, which seems like a carefully selected material. 

I'd be inclined to hire/borrow a set of drain rods and try those. There are more sophisticated drain clearing tools with rotating heads, that cut up tree roots etc. Breaking up the material clogging the pipe is only part of the problem. Unless it's removed it will soon cause the problem to repeat.

As for dowsing, the time I tried it I was over a water supply to a major city, which was three 3 metre pipes. I didn't notice anything. Maybe I wasn't doing it right, or just don't have that particular ability. I don't have much confidence in it.

I have access to both ends.

• First one is the one that supposed to collect water from the ground (due to rains and such). There I can slide something about about 3m deep until it get blocked.
• The second one is connected to a sump (that is drained using another exit pipe). There I can put 4m (slightly more, yes sounds weird).

There is probably a small (eg: not 90 degrees) bend somewhere between both ends.
Neither are completely blocked. There is a little bit of water entering in and existing the other side. However if you put a hose and start filling water it get filled very quickly and then you need a LONG time to get cleared out (should be almost instantaneous).

Pipe is either clogged OR crushed OR destroyed (because of roots, wood or mud).
If it cannot get cleaned, solution is to either replace the pipe entirely or cut it in 2 pieces, unclog the mess and join it back using a sleeve.

[Zenith]

If it's the sort of plastic drainage pipe I've seen, I doubt it's crushed. They are very strong.

Since you have access to both ends, I'd hire some drainage rods and try clearing it with that. If you have tree roots which have grown into it, you won't clear them easily.

[Ian.M]

PVC pipe that isn't draining a kitchen or bathroom (i.e. no fatbergs) doesn't usually block on its own.  Unless some idiot has been pouring cement or similar stuff down it, or something has crawled in there and died, or the grate was missing so its now got a large piece of plastic or wood wedged at a bend, a blockage that doesn't wash away with a pressure washer and drain clearing hose, working from the down-stream end (i.e. isn't mud/silt) implies either a collapsed pipe or a break or crack with root penetration.   Either means extensive digging, and as the whole pipe is of an age, if its got one crack, the rest of the pipe will be as brittle, so unless it goes under a concrete slab, if you don't want to have to fix it again next year, you might as well rip it all out and replace it all.  If you are *really* lucky it might just be a failed joint due to soil settlement + root penetration at the joint, which *MAY* be worth fixing.  Next step is probably see if you can borrow a drain camera and see if the blockage is visible.

Then it give you some kind of circular arc perimeter where the pipe should be. We dig a 2m trench (30-40 cm deep) but couldn't locate it (it took a long time, especially there is small rocks from time to time making thing difficult to carve). Either it's deeper or further from the 2m distance we looked at.

P.S. I believe the minimum depth for drainage is supposed to be 600 mm soil surface to top of pipe.  IIRC shallower pipes need to be capped with a concrete slab or similar.

[Bafflegab]

Tape an Apple AirTag to the end of the tape. Use an iPhone to locate the tag.

[tigrou]

Tape an Apple AirTag to the end of the tape. Use an iPhone to locate the tag.

Somebody tried and it's not so successful (I saw it few days already) :

[Terry Bites]

Put a stake at the endpoints and buy some string?

[halfwave]

Its already been suggested in one form or another but you need a locator. I've worked irrigation, we find control wires using this:

https://armadatech.com/products/product/pro700/

You can either rent one from a local supply house or find someone in irrigation to help.  The trick with PVC pipe is to run a metal fish tape through the pipe and connect the signal generator to the fish. Locator will easily find the pipe. I did it all the time.

[fourfathom]

Its already been suggested in one form or another but you need a locator. I've worked irrigation, we find control wires using this:

https://armadatech.com/products/product/pro700/

You can either rent one from a local supply house or find someone in irrigation to help.  The trick with PVC pipe is to run a metal fish tape through the pipe and connect the signal generator to the fish. Locator will easily find the pipe. I did it all the time.

I have a similar unit and also use the fish-tape method with it.  It does work well enough to be useful in tracing pipes that snake around underground.  It takes some practice though.

[CatalinaWOW]

You know the elevation of the ends.  If it is properly installed it should have a continuous slope between those points and you should thus be able to get the depth quite accurately at points in between.  If you have done this and your existing trench didn't find it there are really only two possibilities.  It was installed with a big sag in the middle and your clog is sediment that has gathered at the low point.  That might have occurred if the original terrain had a dip and someone just laid the pipe before bringing in fill to set the current contour.  Or there is a dogleg bend meaning your trench missed the pipe.  In that case caught debris or tree roots are the more likely problem.

You haven't mentioned the total distance covered.  Is the 7 meters you can probe half the total distance, or some very different fraction?   The answer can put some constraints on the geometry.

In any case, the cheapest solution is more digging.  You don't mention the tools you are using.  A pick or mattock can make digging in the soil type you describe much easier than a shovel alone.   A few weekends should the job.  I have hand dug trenches up to 1.5 meters deep and shallower trenches 50 or more meters long with just a pick and shovel.  The longer trenches were in soil much like you describe.   It just takes some patience and is good for your health.

The next cheapest option would be the finder from Amazon.  It would probably work if the pipe doesn't have a big sag in the middle.  I doubt if it would work in more than a meter of damp or otherwise conductive soil.

Another option which may or not be available in your circumstance is renting an excavator.  In my area rental of a small excavator is a couple hundred dollars for a partial day.  If you have a vehicle that can tow the thing to your location and if you can get such a machine into your problem area it could be an option.   

[calzap]

Tracker I use is very similar to the Digicat.  I don’t have a signal injector for this device and haven’t needed one.  I’m usually trying to locate large wires running underground between panels in different buildings.  It would be inconvenient and disruptive to try to send a signal through the wires anyway.

Mike

[fourfathom]

Tracker I use is very similar to the Digicat.  I don’t have a signal injector for this device and haven’t needed one.  I’m usually trying to locate large wires running underground between panels in different buildings.  It would be inconvenient and disruptive to try to send a signal through the wires anyway.

Mike

My tracker has a clamp-on inductor for injecting a signal into any wires, as well as a clip-lead injector (ground + signal).

[calzap]

Tracker I use is very similar to the Digicat.  I don’t have a signal injector for this device and haven’t needed one.  I’m usually trying to locate large wires running underground between panels in different buildings.  It would be inconvenient and disruptive to try to send a signal through the wires anyway.

Mike

My tracker has a clamp-on inductor for injecting a signal into any wires, as well as a clip-lead injector (ground + signal).

I have an injector that I use with a smaller tracker for smaller wires in walls and ceilings.  Very glad my larger tracker can detect underground wires running between building panels without needing a signal injector.  Saves having to open a high amperage panel and messing with large, stiff wires. To be really safe when opening panels, power to the buildings should be shut down and locked/tagged off.

Mike

[MarkT]

• Using a neodymium magnet + smartphone. I found out that smartphones can sense strong magnets from a distance. Unfortunately, it seems to be a limited range (probably 20 cm max). The fact it's located underground (with soil in between) will probably limit it even more.

Magnetic field drops as 1 over distance cubed as magnets are dipoles, the bigger/longer the magnet the further it will reach, so perhaps extend a NdFeB magnet with some iron/steel rods at each end to improve the magnetic range - this just stretches the dipole longer.

You could also try a standard metal detector if you can stuff metal objects down the pipe!

Soil won't have any effect on the magnetic field unless its full of magnetic material.

[tigrou]

I’ve dealt with this problem more than once.  Feed a loop of 12 AWG (2 mm) wire with insulation rated for wet locations as far as possible, sometimes using a fish tape.  Then power a load of about 1500 W (a space heater) through the wire.  I have an underground electrical cable detector to trace the wire.  Have traced both 120 and 240 VAC.  In the U.S., these detectors can be rented.  Some detectors have a signal injector accessory, so no need to power the wire in that case.

Mike

I have this device already, to detect mower cable cuts. It injects a signal trough the wire using the device on the left (one crocodile clip is connected to one end of the cable, the other clip goes to the ground). The device on the right is for detecting the signal itself.

Would this device work with your trick (using device on the right alone) ?

[calzap]

I’ve dealt with this problem more than once.  Feed a loop of 12 AWG (2 mm) wire with insulation rated for wet locations as far as possible, sometimes using a fish tape.  Then power a load of about 1500 W (a space heater) through the wire.  I have an underground electrical cable detector to trace the wire.  Have traced both 120 and 240 VAC.  In the U.S., these detectors can be rented.  Some detectors have a signal injector accessory, so no need to power the wire in that case.

Mike

I have this device already, to detect mower cable cuts. It injects a signal trough the wire using the device on the left (one crocodile clip is connected to one end of the cable, the other clip goes to the ground). The device on the right is for detecting the signal itself.

Would this device work with your trick (using device on the right alone) ?

Well, the setup with the wire and load looks right.  But I can't say whether your tracker would be sensitive enough.  But give it a try with the injector first.  If that doesn't work, try the load. Be sure the load is powered via GFCI (RCD). I don't have that model of tracker. Even though I have a different brand of small tracker with signal injector accessory, I've never used it for underground detection because my larger one works so well with no need for an injector.

Mike

[Smokey]

...
I have a small (9 cm) PVC pipe going through a garden. It's max 30-50 cm deep...
...I can't locate where it's located underground ...
...
I don't wanna spent so much ...
...

um...  is $9 USD too much?

https://www.harborfreight.com/27-in-round-nose-mini-shovel-with-comfort-grip-handle-64922.html?gStoreCode=577&gQT=1

[Pid]

Leave the original pipe in situ' buy if possible some secondhand solid pvc pipe which is easy to cut and join, hire a trencher.

Use a water level between a couple of metal stakes with a string line to measure down from to maintain a gradient.

For the water level an old hose pipe with a small section of clear pipe added at each end will do.

[antenna]

If you can get a strong neodymium magnet down there via snake, a good compass might pick it up. 

[tigrou]

...
I have a small (9 cm) PVC pipe going through a garden. It's max 30-50 cm deep...
...I can't locate where it's located underground ...
...
I don't wanna spent so much ...
...

um...  is $9 USD too much?

https://www.harborfreight.com/27-in-round-nose-mini-shovel-with-comfort-grip-handle-64922.html?gStoreCode=577&gQT=1

We already spend a whole afternoon digging around the garden and making a 2-3m (30 cm deep) trench without success. It's really hard as there are grass to take care, grit and stones in the soil (blocking the shovel). I have a pick axe and lot of other things to dig but care must but be taken as I don't wanna damage the pipe.

[mikeselectricstuff]

Fill it with oxy-acetylene....