Author Topic: A Water Thumper: Finding buried plastic water pipes  (Read 721 times)

Online awemawson

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A Water Thumper: Finding buried plastic water pipes
« on: April 10, 2022, 02:27:17 PM »
The Problem: I have a ditch and a stream, both of which are crossed by a 25 mm MDPE blue mains pressure water pipe - I'm ditching both water ways and need to avoid the pipes. Both were laid over ten years ago by trenching up to the the banks, and indeed down the banks as far as possible, then the pipe were trodden into the silt as deep as we could. Location known approximately but not accurately.

The Solution: A "Water Thumper" my google research tells me. This is a device connected to the nearest tap, and consists of a water solenoid valve and some electronics to rhythmically turn it on and off like a heart beat. This imposes a pressure wave ( and hence sound) in the pipe which can be detected by a suitable probe pushed into the earth.

. . . . how hard can it be to make that ?

So I ordered some bits off ebay. A pulsing bit of electronics, a water valve, a Chinese 'spy' listen through walls audio detector device  and a waterproof box.

I turned up a socket for the audio device and welded it to a suitable ground spike
« Last Edit: April 10, 2022, 03:14:36 PM by awemawson »
Andrew Mawson
East Sussex

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Re: A Water Thumper: Finding buried plastic water pipes
« Reply #1 on: April 10, 2022, 02:32:46 PM »
The water valve persistently didn't arrive  :( Never mind I had a nice solid brass one intended for a different project - at least test it on the bench with that.



« Last Edit: April 10, 2022, 03:08:06 PM by awemawson »
Andrew Mawson
East Sussex

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Re: A Water Thumper: Finding buried plastic water pipes
« Reply #2 on: April 10, 2022, 02:37:05 PM »
Now the circuit is pretty simple accepting that some one else has kindly programmed the PIC controller. There are two timers controlled by twiddle pots. One for on time and one for off.

I feed the circuit via a diode to save it from reverse polarity issues, and the back emf from the solenoid valve is quenched by another diode. All standard practice.

Andrew Mawson
East Sussex

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Re: A Water Thumper: Finding buried plastic water pipes
« Reply #3 on: April 10, 2022, 02:49:15 PM »
So outside for 'field trials' - literally in this case!

Setting up the device in the lambing field water tap (seven so far but one failed to prosper) sure enough I could follow it's feed pipe easily for the first ten foot or so but then things got complicated  :scratch:

The original trench I'd put in with my trenching machine ( bought wrecked off eBay and renovated for the project) to a nominal 18" but only 12" in places. However in the same trench was a length of 10 mm csa SWA armoured cable and I  think that this was also picking up the thumping and leading me astray.

The pipe went parallel to the ditch then turned 90 degrees across it and it was really this turning point that was vital to find. In practice the sound carried on in a straight line presumably carried by the cable. Finding the turn off point proved extremely difficult.

Now there were only certain points where it could cross the ditch as there is an intervening hedge of hideous Leylandii and it HAD to go between them. So I started on the other side of the ditch and picked up a very faint signal that I duly marked with a spray marker.
Andrew Mawson
East Sussex

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Re: A Water Thumper: Finding buried plastic water pipes
« Reply #4 on: April 10, 2022, 03:05:40 PM »
So how to proceed?

Well I decided that things were still too vague to steam on with the big  8 ton machine, I'd do some tentative scraping with the 3 tonner with a good 'banksman' looking for exposed blue pipe.

We did a really good clean up where the signal was - NO PIPE - we went 6 foot either side - STILL NO PIPE  :scratch:

BUT no water fountains either so perhaps a 'good thing'

Now the 3 tonner hasn't the reach of the 3CX with it's extender-hoe so the spoil got dumped in what would be the wrong place when I recommenced ditching with the big machine. OK put the little one away, get the 3CX out and shift the spoil from the mornings work.

This is where things got VERY messy and the reason is dead obvious when I think about it - hind sight is a marvellous thing.

 . . . . I got the big 8 ton 3CX STUCK FAST - 4 wheel drive, wheels spinning - stuck. It's not entirely obvious from the cab that the wheels are spinning, I thought at first I had some disastrous transmission fault!

 Eventually I had  to 'walk it out' using the back hoe as a pusher but it didn't go easily.

. . . . so WHY did it happen ? Well the field was already pretty soft from rain over the last few days but it was workable. However of course I'd been scooping copious amounts of extremely slippery silt from the ditch, and water from this was migrating to where I was with the 'zero traction' result that I've described.

At this point I gave up, put my toys away and retired for a cup of coffee.

It didn't help that this morning I tested positive for Covid  :bang: But in all honesty so far it just feels like a cold in the head.
Andrew Mawson
East Sussex

Offline Pete W.

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Re: A Water Thumper: Finding buried plastic water pipes
« Reply #5 on: April 10, 2022, 03:22:25 PM »
Hi there, Andrew,

The following might be considered 'off topic' but it isn't really - it's evidence of the effectiveness of using water-borne pressure waves to detect sub-terranean goings-on:

First, a recap. for younger readers:  way back in the early days of U.K. wireless broadcasting, home radio receivers using thermionic valves (a.k.a. 'tubes') had a high tension ('H.T.') 'dry' battery for the anode circuitry and a low tension ('L.T.') battery to power the filaments of the valves.  Strictly speaking, the L.T. supply was a cell rather than a 'battery', it was a 2 Volt lead-acid accumulator in a glass jar with a carrying handle.  This, being a secondary cell, needed recharging at regular intervals.  The charging was usually performed by the local bicycle shop at a moderate cost.

Though this recharging cost was moderate, some householders begrudged it.  There was, on the market, a low voltage dynamo driven by a Pelton wheel turbine, arranged to be connected to the kitchen cold water tap.  This transferred the effort of recharging the battery from the householder's pocket to the Water Company whose pumps would now be the source of the required energy!

The Water Companies weren't at all enthusiastic about this particular piece of technology.  However, it was found that the alternating passage of the Pelton 'spoons' and the intervening gaps past the jet of the turbine launched an audio frequency pressure wave back up the water main.  This signal was very detectable by use of a metal rod placed one end on the bone behind the Inspector's ear and the other end placed on some accessible bit of the water main.  This enabled the Water Companies' inspectors to rapidly 'home in' on the houses where these dynamos were in use.  This sounding rod was/is a standard tool of the Water Companies' inspectors for leak detection.

Your intended set-up, Andrew, seems to be a modern version of the inspectors' sounding rod.

As recently as the 1960s, I remember an occasion when I was working at home (not because of Covid!) when my attention was drawn to a group of men in navy blue raincoats in the road outside my house, each of them carrying a sounding rod and taking turns to try it on the stop-cock beneath the pavement.  This was a group of trainees doing their outdoor practical under the tuition of their instructor.  So, it works.

Andrew, I wish you 'good hunting'.

Well, in the time that I was typing my post ......   :)   :)   :)   :)   :)   :) 
Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest design change-note!

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Re: A Water Thumper: Finding buried plastic water pipes
« Reply #6 on: April 10, 2022, 03:31:25 PM »
That's an amusing tale Pete - I'll give you another!

Back in that era some people were using the voltage difference between actual earth and the neutral line via a rectifier to charge their accumulators. This had started back in the DC distribution days when of course the rectifier wasn't needed, but the supply companies had the habit of sometimes reversing the polarity  to dissuade people from the practice by destroying their cells! 

Come AC distribution people soon found that if they were sufficiently far from the neutral / earth link (so perhaps at the far end of a street) there was enough voltage difference to get those lead acid cells charged!
(but you did need the rectifier)
Andrew Mawson
East Sussex

Offline vtsteam

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Re: A Water Thumper: Finding buried plastic water pipes
« Reply #7 on: April 10, 2022, 06:44:17 PM »
Andrew I think that's a really clever idea using the thumper you made to trace the line. Very cool!

Sorry you got stuck, and VERY sorry you have contracted Covid!! I hope you will come through this with just the head cold symptoms. I guess it's inevitable that we will mostly all get it eventually. Our family has managed to avoid it so far, but I can't imagine that will continue forever, as we all get closer every day to resuming normal activity and increased exposure. There's just the hope that the variants have become less virulent and vaccinations may help reduce severity. Anyway, keep your chin up, and please get better soon.  :beer: :beer: :beer:

I do want to hear you trace that water line to the point you need  :dremel:
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

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Re: A Water Thumper: Finding buried plastic water pipes
« Reply #8 on: April 11, 2022, 02:28:08 AM »
Thanks for the kind words Steve, much appreciated.

Well I’ve woken up this morning to think “what is all the fuss about?” No headache, very minimal sore throat, and as yet no sneezing unlike yesterday! Mind you I’ll probably get my ‘come upance’ later as it develops. So although we’ve put the quarantine flag up and are avoiding folk, I’m going to carry on as far as possible ‘normally’ which today means under the thumb and continuing fixing her poly tunnel !

Andrew Mawson
East Sussex

Offline Sea.dog

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Re: A Water Thumper: Finding buried plastic water pipes
« Reply #9 on: April 11, 2022, 03:52:53 AM »
Bad luck with the Covid, Andrew, but almost inevitable now.
I'll add that a positioning a long screwdriver against your ear and prodding various spots on engine is also a time-honoured way of detecting nasty goings-on inside.

Offline mattinker

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Re: A Water Thumper: Finding buried plastic water pipes
« Reply #10 on: April 11, 2022, 06:36:36 AM »
Thanks for the kind words Steve, much appreciated.

Well I’ve woken up this morning to think “what is all the fuss about?” No headache, very minimal sore throat, and as yet no sneezing unlike yesterday! Mind you I’ll probably get my ‘come upance’ later as it develops. So although we’ve put the quarantine flag up and are avoiding folk, I’m going to carry on as far as possible ‘normally’ which today means under the thumb and continuing fixing her poly tunnel !

The current strain of Covid is much milder than the one I had! Three weeks of high temperature! Literally ten times longer than now!  It's no fun, but you should be over it soon!!

All the best, Matthew

Offline Pete.

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Re: A Water Thumper: Finding buried plastic water pipes
« Reply #11 on: April 12, 2022, 02:41:09 PM »
My wife just had  week of it, a sore throat and feeling a bit grotty but nothing worse than that. I hope you fare as well Andrew.

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Re: A Water Thumper: Finding buried plastic water pipes
« Reply #12 on: April 12, 2022, 04:12:21 PM »
Thanks Graham, Peter and Matthew - I feel a fraud as really I'm not showing any symptoms now, but the wife has a bit of a persistent cough.

Certainly very grateful for all the rapid work the Government and Medical Agencies & firms did in the early part of the pandemic to get us to the point of being now thrice vaccinated and resisting the worse effects. Cast your minds back a couple of years when people of my age group were being admitted to intensive care in huge numbers often with sad outcomes.
Andrew Mawson
East Sussex

Offline Pete.

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Re: A Water Thumper: Finding buried plastic water pipes
« Reply #13 on: April 12, 2022, 06:06:18 PM »
Very true and it wasn't only the older generations and the vulnerable, we had two in our office hospitalised, one seriously. Both in their 30's and one a fitness fanatic.

Offline Spurry

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Re: A Water Thumper: Finding buried plastic water pipes
« Reply #14 on: April 14, 2022, 06:13:48 AM »
Hope you are feeling somewhat better now. Came across this video and thought it would be just the job for you. No idea if anything like this is available in the UK, but you could always knock one up.:)

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Re: A Water Thumper: Finding buried plastic water pipes
« Reply #15 on: April 14, 2022, 10:36:17 AM »
Pete thanks for that - that is an amazing set up and brilliant for safe digging - just what I want ! That would make short work of my issue . . .

 Now lets see . . . petrol pressure washer (got!) . .  . one of those lorries councils use for sucking out road drains . . .we always used to call them 'Dirty Lizzies' in our family

mm . . . I'm sure something could be knocked up pretty quickly  :clap:


As for the covid thing - apart from a slight sore throat I'm fine and as I said earlier I feel a bit of a fraud ! Due for another test tomorrow (Friday) morning.
Andrew Mawson
East Sussex