Gutters can easily be checked for leaks on a rainy day. If it’s not raining, sending water along the gutter and down the drainpipe using a hose is effective. Gutters should be repaired when weather is warm, dry and likely to remain that way overnight.
The affected area should be thoroughly cleaned and left to dry naturally. A wire brush will remove any loose bits from rusted gutters, then use denatured alcohol to clean the area.
Apply a bead of caulk to the leaking area will repair minor holes and cracks. Use a flexible putty knife for a smooth finish. Roof repair cement and a metal or fabric patch will be required for holes in metal gutters.
Spread a decent amount of the cement over the section to be repaired before pressing in a piece of roof repair fabric or metal flashing. Top with another layer of cement. Your patch, if metal, should be the same type of metal as the gutter itself.
Self-adhesive patches are a good option for repairing plastic and metal gutters. Be sure to remove any bubbles and kinks from the patch as you apply.