I HAVE SEWERAGE COMING OUT OF MY DRAINS BUT CAN NOT LOCATE A MANHOLE COVER ON MY PROPERTY OR MY NEIGHBOURS PROPERTY,DOES ANYONE KNOW HOW I CAN FIND OUT WHERE MY MANHOLE SHOULD BE. IT COULD POSSIBLY BE COVERED IN TARMAC AS THE PREVIOUS OWNERS HAD THE DRIVEWAY TARMACCED. IS THERE SOME SORT OF DEVICE YOU CAN USE TO LOCATE IT? THANKS JOANNE