Mac users interested in Gratis epanet generally download:
EPANET is a public domain hydraulic analysis package for water supply networks. If the drive/path you're looking for is not directly accessible from EPANET (this could happen e.g. with network drives), try winecfg.
Requiremesnts: Mac OS X 10.6 Snow Leopard with an Intel processor. 10.5 and earlier versions are not supported.