Water filters - am trying to supersave...

Hello all -- this is my first post......Just bringing my caravan out of winter, all new to me disinfecting pipes etc. Have just bought a new water filter for when the pipes are clean. It seems to me expensive and not very 'eco-friendly' if the whole unit of the Carver Crystal filter has to be replaced every 30 days use. Is there a way of keeping the housing and replacing the filters inside please