It may not serve your property, could drain neighbouring properties, or carry a spring away from the buildings to the storm sewer, any manner of things. Unless you can prove it's redundant though, the Water Co will need to see it's been protected.
Unfortunately the Water Company maps arent always accurate, having seen the map for my local area, I could point out a host of mistakes, missing runs, wrongly sized pipework, and my parents estate is missing completely, (roads etc are there, but no sewers marked. Again, I know they're there as I saw the Builders put them in on the latter stages!)
