Steam boiler feed water

bruce_21

Went to see an old client's newly bought property. Serious problems with hard water in the sinks, toilets etc. So they want a softener installed. They have a steam boiler to heat the place. I remember seeing a discussion here where the question of supplying a steam boiler with softened water went around, but can't remember the upshot or find the thread in the archive. Should I supply the steamer with raw water at 20 grains of hardness or feed it the soon to be softened water?