tweake:
i had a split in the main water pipe a few months back. the interesting thing was that it must have been on going for quite a long time as the water flow carved out a tunnel in the dirt. i think the split opened up depending on ground movement, which is why it was never noticed for a long time as water usage didn't change a lot.
We had a leak that was going through about 6L a second. We didn't know until after an actual reading and a high four figure water bill.
Took about three weeks to identify where it was and we needed to divert the main line as the leak was under the neigbours concrete patio. We still ended up having to cut a big slice through our concrete driveway. If it wasn't for the water bill we would have no idea of the leak as we have volcanic rock with ample drainage beneath us.
Watercare refunded most and credited our account for what we did pay so we haven't had water bills since.