Most gutter calls start with one sign seen from the ground. Each sign points to a short list of causes, and a repair visit checks them in order.
Dripping at a seam or corner
Sectional gutters are joined every 10 or 20 feet and at every corner; seamless gutters are joined only at corners and end caps. Sealant at those joints dries and lets go over the years. A repair cleans the joint and reseals it, or replaces a corner piece. If the drip is at the downspout outlet, the outlet's seal is the usual suspect.
A run that sags or pulls away from the house
Gutters hang from hangers fastened into the fascia board and the rafter tails behind it. A run sags when hangers have pulled out, when they were spaced too far apart for the load of wet leaves, ice or water it carries, or when the wood behind them has rotted. Rehanging on fresh hangers fixes the first two; rotted wood has to be replaced first, or the new screws have nothing to hold. See fascia and soffit.
Water spilling over the front
Usually a clog, in the trough or in the downspout. If the gutter is clean and still spills in a hard rain, it may be pitched the wrong way, too small for the roof section, or short a downspout. Why gutters overflow walks through each.
Water behind the gutter
Water running down the wall behind the gutter, or stains on the fascia, often means the roof edge does not lap into the gutter: a missing or short drip edge or gutter apron. It can also be a gutter hung too low on the fascia. The fix is a strip of flashing, not a new gutter.
Repair or replace
Repairs make sense when the trouble is in one place. When seams leak along the whole run, the metal is rusted through or dented in many spots, or the gutters have reached the age the material is expected to last, replacement usually costs less over the next decade. InterNACHI's estimate for aluminum gutters is 20 to 40 years or more, and for galvanized steel about 20. New and seamless gutters