OK, here is what I know.
All persons involved should know the following:
On plastic pipe lines leaks tend to grow quickly in soil with any abrasives in it such as sand, quartz, etc. As water escapes a jet of water “roils” the abrasives in the soil which in turn eat away at the plastic so that the plastic is in effect “sand blasted”. By our experience small leaks will open up to a sizeable leak within 2-3 months maximum. CONCLUSION – Be patient, walk the line looking for evidence of leak (see below).
Become aware of and train yourselves about the evidence of leaks on soil. Make your own photographs and make sure your people are always on the lookout for the following:
1. Water rising to the surface and then moving downhill takes lighter materials and organic detritus away leaving heavier materials near to the point of exit such as a whitish or clean looking sand.
2. Leaks carry materials away so there are almost always depressions left.
3. Water flows downhill so inspect low lying areas carefully. Do not assume pooling water is from lawn sprinklers, agricultural watering, or rain. You must walk through the puddles to see if there is a continuous flow from some direction, follow the flow to find the source.
4. Become aware of things that leak by nature and enact program to eliminate those frequent sources of leaks. Largest villain is gate valves. Simple cheap gate valves are intended for service only, not on/off service for which you need a soft seating type valve. All knife gates will leak if used for on/off service, you must eliminate them and any other fitting or valve that tends to start leaking quickly.
5. Leaks on hard ground with very slow percolation rates show up on the surface quickly.
6. Leaks in soft ground with high percolation rates can hide for long, very long periods of time.
7. Leaks under roads, concrete, and other hard surfaces travel the route of least resistance, not the shortest path. In other words, it may be 10 feet from the edge of a road to the leak, but that leak may travel 100 feet downhill through a porous area before going to the edge of the road.
8. Loose asphalt indicates a leak. Asphalt will seal off water very effectively. A leak will separate the asphalt from the rock base causing a bubble in the road that moves when pressure is applied. Some very thick rooting grasses will do the same. So look for high spots that move.
9. Some leaks are just buggers, especially if they are aimed downwards and in loose soil. In those cases there may be no depression, no whitish sand, and no other simple evidence giving visual clues.
Now, as far as tools:
Use a stethoscope or small piece of tubing or pipe to check valves for internal leakage. Any leaking valve will make a hissing sound. I believe rubber is the best transmitter of sound from an object to the ear.
Scan the internet doing a search for the keywords. You will find many great claims so be careful but ultrasound and infrared are good tools. I especially like the infrared.
Best tool will always be an observant careful and patient person walking or driving the line. Not all people are suited for this.
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PUMPDESIGNER
