Different pipe materials and different pipe diameters transmit leak sounds down their pipe walls very differently:

Iron Pipe	6 inch	1000 — 1200 ft
Iron Pipe	12 inch	800 — 1000 ft
Iron Pipe	24 inch	600 — 800 ft
AC Pipe	6 inch	800 — 1000 ft
AC Pipe	12 inch	700 — 900 ft
AC Pipe	24 inch	400 — 600 ft
PVC Pipe	6 inch	400 — 600 ft
PVC Pipe	12 inch	200 — 300 ft
PVC Pipe	24 inch	100— 150 ft
*For 5 gal/min leak at 60 psi pressure

The service line material is also very important when listening at meters or curb stops:

Copper Tubing	600 — 1000 ft
Galvanized Steel Pipe	800 — 1200 ft
“Poly” Plastic Tubing	50 — 100 ft
*For a 2 gal/min leak at 50 psi pressure

If the distribution system experiences main breaks (5 to 10 gal/min or more) at certain times of the year and the mains are iron pipe or A/C pipe, then a “Hydrant Survey” can be effective and an efficient use of time. Listen at every hydrant in every block. If there is no hydrant for 500 ft., then choose a main valve.

If the distribution system has PVC mains and copper services, then an “Every Meter and Every Valve Survey” may be necessary. Particularly if the system experiences small leaks at the corp valves (taps into mains).