QUOTE(Pillowgirl @ Sep 14 2018, 14:25)

Or there is a rupture in the pipe and it's leaking.
That's most likely what's happening. There could be a break in a pipe somewhere, possibly underground.
This is interesting.
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The Toilet?
Generally, the culprit is a toilet. Since you live in the home, and are responsible for its day to day upkeep, you have to pay attention to whether a toilet, or some other water source, are running constantly. A drip in a sink won’t markedly affect your water bill, but a toilet that is running, even one that is barely noticeable, can increase your bill tens of thousands of gallons (and $100s of dollars) over a very short period of time.
Toilets can have this happen to them at any time, and keeping an eye (ear!) out for signs of a running toilet is an important part of living in a place of your own. Be on the lookout for a constant or intermittent sound even when the toilet isn’t–and hasn’t been–in use. These noises are always a good indicator. You can even play detective yourself. But the reality is sometimes the trickle in a toilet is so quiet that the first thing you will notice is, well, a high water bill.
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When your toilet or other water devices use excessive water, your meter will spin (and spin and spin), costing you lots of money before you know it. Be watchful for signs of running toilets and take immediate steps to mitigate your loss (e.g., turn off the toilet’s water supply).