Locating Leak In Underground Poly Pipe

[echnidna]

I have a pressure leak in an underground polypipe.
Can't find any obvious wet spots along its 100 metre course Though I'm not exactly sure of its precise position.

Any way of locating the pipe and leak (short of digging it all up)

[Ironwood]

Funnilly enough I am in the same predicament myself at the moment. I am on a 9 acre block, and there seems to be poly water pipes going in all directions, we always find a couple when digging a trench, or even when putting post holes down. I walked everwhere today with no luck finding a leak. I would have expected a green patch, as the grass is starting to brown off here now.
When we bought this place I got a cable locator guy to come and find all the power and phone cables, (drew myself some mudmaps) when he was here he said he could trace poly water pipes. I think he may have put an electric charge into the water and then his machine could pick it up. I'm kicking myself now for not doing it at the time. Will probably have to pay him to come back again now.

[outback]

Cos' I'm an ijit and you're not Bob;

How do you know you have a leak?

Is it mission critical to know until you bust a fitting apart, which is the most likely place for a leak?

If all else fails can it wait until the grass is greener on the other side?

[Stuart]

Radioactive tracers :D (Well, it would work....)

[echnidna]

Cos' I'm an ijit and you're not Bob;

How do you know you have a leak?

Coz the header supply tank water level falls daily even when no water is being used. If I turn off the pressure system the tank level don't fall at all. This leads me to conclude it is a pressure leak

Is it mission critical to know until you bust a fitting apart, which is the most likely place for a leak?

Nope, but given the length of run there might be a few buried fittings

If all else fails can it wait until the grass is greener on the other side?
The grass has never gone brown here over the past 5 years.

[Jarrada]

Had quite a few of these in my time, can be very hard to find, The best way I have found was to wait a couple of days then look for a greener spot, If you are in sandy or soft ground the leak will increase with pressure and will blast the soil away from the poly pipe and in most times you will be able to see a very wet spot or the spray of water shooting up into the air.. how far is the poly down ? through stony areas the poly scratches, we have found about 10 years down the line after the poly has been laid the leaks seem to come thick and fast