Changing to combi from gravity feed do I need a new pump?

All your existing control system will be scrapped as well as your hot water tank. Everything needed including the pump will be provided inside the combination boiler. This answer assumes you mean a combination boiler(sealed heating system and instantaneous hot water)

David
October 2010

can't have pump

p bonney
September 2010

your combi's comes with a self contained pump ,and a diverter valve to change from hot water to central heating

wirecutterman
September 2010