I posted the following in another thread where the OP heard water running. It might help you during your troubleshooting:
"Check your water meter and see if the water movement indicator is spinning. Even a slow leak will spin the water movement indicator like one revolution in 3 minutes for example. But to hear water running, it would have to be a fairly fast leak. Hidden leaks can happen if they are under ground or under a concrete slab. To get a feel of how fast the water movement indicator does spin, turn on a faucet in your home and check it. It will be spinning like crazy. Lower the flow from the faucet so it is just a slow stream and look at the water movement indicator. It will be spinning slowly. If your water movement indicator does not spin at all with all faucets turned off, then you don't have to worry about a potable water leak."
HRG
"Check your water meter and see if the water movement indicator is spinning. Even a slow leak will spin the water movement indicator like one revolution in 3 minutes for example. But to hear water running, it would have to be a fairly fast leak. Hidden leaks can happen if they are under ground or under a concrete slab. To get a feel of how fast the water movement indicator does spin, turn on a faucet in your home and check it. It will be spinning like crazy. Lower the flow from the faucet so it is just a slow stream and look at the water movement indicator. It will be spinning slowly. If your water movement indicator does not spin at all with all faucets turned off, then you don't have to worry about a potable water leak."
HRG