The Basementsaver WP-Series water powered back sump pumps are available at the Basementsaver Discount Backup Pump Outlet at http://www.basemetsaver.com
These emergency backup pumps are very easy to install and much more efficient than the other models I've seen. They actually remove up to 2 gallons from your sump for every gallon of city water used (with a 10ft lift to discharge).
The Basementsaver HP-Series water powered backup sump pumps come with "approved" backflow protection and can even be used with very high pressure water systems up to 150 psi.