I'd soak it in in CLR, or vinegar to remove the calcium deposits. Something is reducing flow, increasing pressure inside the unit.
A bit of wire brushing, sand papering and solder as suggested first would be a start. If stainless then silver braze.
Wes
-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller