I have about 7 meters of PVC pipe connected to the water meter. Some of this pipe is above the meter level so some air sure gets trapped inside.
Is it possible that the air in pipes expand and contract changing the meter reading? In a 24 hour period, my meter registered 50 liters of water. I checked the pipes many times and haven't found any leaks (the pipes are exposed). At that rate the leaking should be pretty visible, right?
I was watching the meter now (noon, full sun) and I could see it registering some hundred ml in a few minutes, but no drops anywhere.