The old-fashioned way is to lift sewer manhole covers. Sewers (other than rising mains) are almost always straight lines between manholes to minimise blockages.

Potable water is more difficult as they can go anywhere. I have not used acoustic detection myself but it does work, in the right conditions. https://www.aasdetectionsolutions.com/sensit-techn...

Fibd someone for whom divining rods work.

Seriously.

Many people will pour scorn but IME, it works down to about 2m cover.

Mine are just welding rods, but they find all sorts of pipes and cables, not just metal.

Works for some people and not others and I would never say its 100%, but tends to find false positives. The bigger the pipe the better.

But you need to find the right person.

Many of the water company techs swear by them.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

GPR and divining rods are your best bet. I know water departments use acoustic devices to find leaks, and they might work for finding the line if it was flowing water, but it would have to be when it was quiet (late night/very early morning).

We use divining rods in conjunction with other methods when working within the roadway because nothing works 100%. We've hit empty plastic conduit when drilling, but the GPR couldn't find it even after we knew it was present. A local city's water department only uses divining rods to find their pipes. I've talked to many utility locators that have them in their trucks. But as LI notes, they don't work when the line is very deep, and they don't work for everyone for some odd reason. Divining rods work for me but not one of our employees. I prefer to use the ones that are brass with copper handles as they are the most sensitive (you can get them on Amazon, if that's an option for you). It doesn't work on plastic without some flowing water.

Don't forget to ask local water and sewer authorities. And if there are manholes, you definitely should be popping the covers to check where everything is going.

yah, another believer!

As I said mine are just welding rods bent into a long L shape. I've seen people use them with plastic bic biro pen body as the "grips" but I just have a very light grip with two fingers.

I personally think its something to do with local magnetic disturbance of the duct so doesn't always need flowing water IME.

Power cables are very clear action, small deep plastic pipes >2m deep you probably won't find. but combine it with other detectors and you end with some unknown question marks to dig more carefully / hand dig

Best thing is they work anywhere - flameproof, need no power supply and somehow just work in the right hands. I carry them with me anytime I go out on site.
But for some reason it doesn't work for everyone.

In any pipe that is running "full" like a water main, you won't hear a thing. And even gravity sewers unless there is some sort of flow disturbance.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Quote (LittleInch)

I personally think its something to do with local magnetic disturbance of the duct so doesn't always need flowing water IME.

I agree, but OP was asking about PVC pipe, which I have not been able to find when it's just an empty conduit. Flowing drinking or sewer water, yes.

Divining rods are even in the Field Engineer's Manual by Parmley, P.E., 1995. Although I have read someone's book review stating that "Pseudoscience or "magic" have no place in an "engineering manual".



I've seen one contractor find an electrical duct bank they needed to tie into without plans using those rods. I've found a homeowner's (illegal) underdrain tie-in to the town's drainage without knowing it was there. It has saved my butt more than I can count by avoiding drilling through unmarked utilities. All earthwork contractors, public utility locators, and drillers I've talk to about it agree they work! The private utility locator guys give me crap though.

In a pinch, I'll use the handle from a bucket, bend it into an L, and use the plastic piece as the handle for the divining rod. It works pretty well, but not as good as my brass rods.

I've found empty plastic pipes alright plus fibre optic cables, but they might have been armoured, but the really small ones are a bit hard.

That drawings a bit over engineered for me....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

I agree. It's great that someone had the guts to put it into an engineering textbook, knowing that there are a lot of non-believers.

I'm assuming you have already discussed with the "DigRite" utility locate services. I've watched many excavations where the excavator operator scrapes back the soil about 1 foot at a time, the laborers then probe with a utility probe rod to see if they can detect anything. This process continues until the pipe is detected within a foot or two, and the laborers start shoveling by hand.

Another option is to use a "vacuum" truck. The ones I have watched spray a jet of water into the soil, then vacuum the wet soil slurry into the holding tank. You end up with a shaft, about 8-12 inches in diameter down to the top of the pipe, if you are aligned properly. You can test lots of locations with the vac truck in a fairly short time.

The use of divining rods, "witching" in the midwest, can be quite subjective based on the individual's biochemistry. It works great for me, but I had a boss that it didn't do a thing when he tried. I even heard about one individual that would stomp his foot on the ground when the wires turned, until they turned back. The number of stomps before the wires turned again was the approximate depth of the pipe in feet.

For nonmetalic pipe, that is accessible, Push a fish tape (a snake cam, or 22 ga wire tapped to a hydraulic sewer rodder also works).
Then connect a signal injector. The signal can be traced with a standard underground locating device

That implies

A) access into the pipe
B) you know the pipe is there.

I would say 95% of the time neither would apply...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Most of the pipes I am interested provide some hint of their existence. it is often the path I can't guess. We learned our lesson about MDPE gas pipes without tracer wires, don't do that.

I hit a gas line (50 psi) that had been pressurized the week before, and was not marked (bored beneath pavement so no joints to tell us it was there). The guy from the gas company said the locators wouldn't even have the paperwork on the new line for another 6 months.

Thanks for all the very useful replies! I will definitely check LittleWheels' link detector, just hope it isn't too pricey... I wasn't expecting the advice on the divining rods , I am usually on the skeptic side of things... but they're cheap so why not give them a try... TigerGuy I feel your pain... hope you solved it.

"There is nothing in the desert, and no man needs nothing."
CEDEX Madrid graduate.
Private construction materials lab

If there isn't a tracer wire for the water line, it can be very difficult, and finding it may be more expensive than fixing it after you find it 'the hard way'. For concrete sewer lines, if your backhoe operator can't find it without damaging it, you need a new backhoe operator.

That detector looks like an acoustic version of a GPR. Needs a lot of points to map an area.

Also no price which always makes me nervous....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.