Basementsaver Sump Pumps & Backup Sump Pumps Outlet offers a range of high quality water powered backup sump pumps at http://www.basementsaver.com

For normal city water pressure (40-100psi) choose from 3 models:
Basementsaver WP1 water powered backup sump pump - pumps 900 gph
Basementsaver WP2 water powered backup sump pump - pumps 1,400 gph
Basementsaver WP3 water powered backup sump pump - pumps 2,000 gph

The company also offers Basementsaver HP-Series water powered backup pumps - intended for high water pressure systems (75-150psi).

Additionally, if your water department insists on 'approved' backflow prevention the WPA-Series and HPA-Series pumps include an integrated AVB.