As a matter of interest: I see from the MSD sheets that Ilford incorporates a water softening agent, Sodium Tripolyphosphate, in all of their packaged powder developers.(posted 8089 days ago)As previously posted, some types of water hardness, classed as 'temporary hardness', can be removed or reduced by boiling the water.
Hardness due entirely to Carbonates falls into the category of temporary hardness.
In addition, boiling the water will remove most dissolved gases. (In fact, the removal of CO2 from water by boiling is what causes the carbonate content to be precipitated out, so reducing the hardness)
I'd be more concerned about the residual pH of the water supply, after boiling, though. Does your water authority give out this figure? If the water is acidic, then this will reduce the activity of any low alkalinity, i.e. fine grain, developer. Drinking quality water really shouldn't have a pH lower than 6, or much above 8.