Water supply problem.

[dave21478]

Hi,

Not me, but some people I know, who have asked me to investigate / repair.

They live in a very remote location. On their land, maybe 1/4 mile from the house is a concrete tank set into the hillside. This is filled by natural springwater. As a side note - access to this tank is almost impossible. Its a harsh trek on foot, and getting "big tools and stuff" there would be nigh on impossible. God-knows how that tank was ever installed!

There is a take-off pipe in the tank which is buried underground and runs down the hill, feeding the house by gravity. Its not a straight decent to the house, the path of the pipe drops then rises over a small valley, but overall the house is lower than the tank.

They arrived after a long period away to find no water at the house, and the tank water level at the level of the takeoff pipe. Its been hot and dry here, with no proper rain since July, so there were doubts as to the springs ability to provide water. Before they asked me, they got a farmer with a 2000l bowser and long hose to refill their tank. Seemingly, this water "dissappeared" over the course of a day, with none getting to the house.

It would seem very obvious to me that there is a break in the pipe between tank and house, which would explain the 2000litres vanishing, and would explain why the tank level stays at the level of the take-off pipe. The water is just draining away into the land, not allowing the tank to fill.

What would you do? Im at a loss to come up with a workable solution. The routing of the pipe is completely unknown. Its unknown what depth its buried at - all I can say is that it crosses steeply sloping woodland that is almost impassable on foot, never mind with any kind of machinery, for approximately 1/4 of a mile. Laying a new pipe to the tank would be best I suppose, but this would be such a monumental labour effort that Im just not capable of doing it in a reasonable timeframe.

A vague hope is to disconnect the feed into the house and blow compressed air up the pipe. If I block the pipe at the tank, there is a very faint possibility of hearing air escaping and pinpointing the break.

Any other usefull suggestions? Preferably one not involving spending a week neck-deep in brambles trying to dig a trench down a 40 degree slope.

[Théière]

Hi Dave,

You could try PM'ing Chrish or Poolguy, they have specialised leak detection equipment.

 

[powerdesal]

[quote user="dave21478"] it crosses steeply sloping woodland [/quote]

Tree roots and buried pipes are a bad mixture unfortunately. Even if you find the leak now the same will probably happen again and again. A new pipe is probably the answer but a good pipe route is going to be the problem

[La Guerriere]

If it is that overgrown, just lay a new plastic pipe on the surface farmer-style, it will soon disappear

[dave21478]

Yes, the break is very probably due to tree roots, as the forestation appears to have grown up in the last 20 years or so and seemingly the tank and pipe pre-date that.

Laying on the surface isnt really a good idea as the water in the pipe will be heated by sunshine in summer and will freeze in winter.

[BIG MAC]

What size is the pipe and what is it made of?

Does the tank belong to the property?

If the farmer can gety a 2000ltr bowser to the tank surely a mini excavator could do likewise?

If replaced in Polythene then tree roots shouldn't be too much of a problem other than pushing the pipe out of the way.

If you are in a predominately clay area and there has been a lot of soil shrinkage then this may have been sufficient to fracture the connection near the end of the pipe.

2000 Ltrs just running away would normally be visible in a nice verdant area look for lush grass etc. this may indicate where the leak is

 

[freddy]

Another thought - there are cameras on the end of cables for looking at the pipe for breaks and also tracking thingies where you run the cable through the pipe and then track the pipe overground with another thingy that looks like a metal detector.

Presumably you can hire them - can't help with french for thingy as not sure what the right names are in english but Dynorod etc, use them the whole time.

As a further thought it might be possible to run a smaller plastic pipe through the existing pipe, depending on the diameter,  as a kind of liner but you would have to do some thinking about how to push the pipe through that length. I would imagine you would need to use compressed air to blow a cork on a piece of string through, use that to pull through a thin steel cable and use that to pull through the liner pipe with a carefully constructed pointy end to get past any partial blockages.

[BIG MAC]

What yourefer to is called a sond and can be picked up by a CAT scanner. The sond is a signal generator and is inserted into the pipe this is usually for drainage work on larger bore pipes unlikely to work on a 20mm pipe over a great distance.

The tank fills from a spring if the water table has dropped will topping the tank up not simply make it flow back in the opposite direction?

 

[Alane]

I may have misunderstood but you say the supply pipe drops then rises before the final drop to the house. If the spring has run dry the water in the pipe may have drained out and you now have an airlock. Is it possible to pump water into the outlet of the cistern to force it through the pipe?

The 2000l may, as has been suggested have drained back into the dry spring, and no water is coming through the pipe due to the airlock. Just a thought.

[dave21478]

Thanks for the suggestions so far.

The tank and source is part of the property. There is an access road maybe 60 or so meters above the tank, so the bowser was parked on the road and a long pipe dropped down the slope to fill the tank. I own a mini excavator myself, and can tell you that attempting to get it into the area is very likely to end in tears. When I have the time, I plan to do a full scout of the area on foot to look for other access points and see if any obvious problems are apparent.

Looking into the tank, the internal layout would suggest that its not likely for the water to flow back into the spring if its dry.

I had a thought today, but was too late to implement it, but I plan to block off the take off pipe inside the tank. This will tell me definately whats happening. If the water level stays the same or drops, the problem is with the source, if it fills, the problem is with the pipe.

The takeoff pipe looks to be a flexible pvc type pipe, maybe 40mm diameter, although the only section visible is the first 10 cm inside the tank. once it passes outside, I have no idea if this is what continues down the hill or not. I cant see what kind of pipe it is at the house end without a bit of digging first. Thing is....isnt a pvc pipe a little bit modern? if this system was installed at least 20 years ago according to the owner, I would have though plastic piping like that unlikely? How long has this sort of thing been in use for? My sisters farm had a similar system that was left to rot once mains water was connected years back, but the piping is heavy lengths of cast iron pipe.

Some kind of probe or endoscope would be great, but I doubt if its possible to use one in such small piping and over such a long distance?

Re an airlock, I have considered that too, but im not sure exactly how the pipe drops and rises, so cant say for sure if an airlock is possible.

Pumping in compressed air still seems my only real option for now, but I wonder if my compressor is up to it? its a 2.5hp hobby thing, so I think it may struggle to fill such a volume, especially if the pipe is broken, I doubt it will generate enough pressure quickly enough to potentially show up where the break may be.

[Chancer]

Dave, an airlock seems likely although it could also be a result of a minor leak and drying up of the spring.

I would pump water from the house up to the tank ideally using a surpresseur (the compressors used to augment low mains pressure or pump from a tank) which can be bought cheaply from the sheds, alternatively you could rig something up from your compressor and a redundant gas bottle (I know you are capable and competent).

You didnt mention the fall from the tank to the house, you will need one bar (14.7psi) for every 10 meters of vertical elevation to the tank.

You will first need to calculate/estimate the volume of water to refill the pipe along its full/ estimated length, hopefully you will not need the bowser again. Then get pumping.

If it all dissapears to nowhere then keep the pump running, fit a pressure guage in the discharge line and read the dynamic pressure, if it is for example 2 bar then the pipe will have fractured plus ou moins 10 metres higher up the hill.

Good luck and let us know how you get on.

[dave21478]

An excellent suggestion! thankyou.

I dont know what the height difference is between tank and house, as one is not visible from the other due to the trees and I have been unable  find a detailed enough map of the area. The pipe cuts across the small valley where the access road winds perhaps half a mile the long way round.

When I get the chance, I will have a wander around the valley on foot, which will give me an idea of height differences, and I might just stumble across a broken pipe sticking out the ground with springwater running from it!

The local Mary has been very sympathetic to the situation and has given them keys to the swimming baths in the nearby village so they can use the shower facilities. I have dropped off a couple of big containers at the house for drinking water too, so they are not in too much of a pickle, but obviously this will need fixed as quickly as possible.

[Chancer]

The Blue IGN series of maps, roughly equivalent to the landranger ordinance survey maps, cover all of france and have contour lines at every 5 metres marked on them, you should be able to find the elevation difference from them.

Failing that you if you can see the property from the tank or somewhere level with it wih the aid of a spirit level, sighting stick and an a protractor you can calculate it with trigonometry.

Or borrow someones hand held GPS [:P]