|The following is based on Fallout: New Vegas cut content and has not been confirmed by canon sources.|
This purifier would provide clean water to Underpass, if it were functional. Whoever assembled it had no idea what they were doing - many parts are connected incorrectly or hooked up backwards. Someone with the proper knowledge could easily get the purifier operational.”
Underpass was going to be a settlement north of New Vegas, but was cut for unknown reasons.
There would have at least been Carlyle St. Clair's house, and according to the cellname, a purifier close by.
Underpass was cut from the final version of Fallout: New Vegas.