If only in for a year it is probably still under guanantee. Whoever installed it should know. If not a supplier who stocks it will know.
A pump will make noise when the shower is on. They usually are run off mains supply so lime scale should not be involved. Long use for a shower could cause it to struggle. Depends on its abilities (Quality) to begin with. Limit showering time to 10 mins to see if unusual noise stops.
Vincent
September 2008