Occasionally, gutter seams or joints open, producing major leaks. Knowing how to repair plastic gutter seams early on reduces the chance of further damage and, possibly, a major repair. Repairing the seal in a plastic gutter seam will keep the water from pouring into your woodwork.
Wash the seam area of the gutter.
![Wash the seam area of the gutter.](https://www.dummies.com/wp-content/uploads/82840.image0.jpg)
Clean the repair area to remove any grime or debris.
Prepare a tube of exterior-grade polyurethane caulk.
![Prepare a tube of exterior-grade polyurethane caulk.](https://www.dummies.com/wp-content/uploads/82842.image2.jpg)
Cut the tip off the caulk tube nozzle at a point where it produces a bead large enough to fill the crack. Start small — you can always make the hole bigger. A 1/4-inch bead is large enough for most cracks. After you cut the tip, you have to puncture the seal in the end of the caulk tube using a stiff wire or long nail.
Apply a bead of caulk along one of the cracks.
![Apply a bead of caulk along one of the cracks.](https://www.dummies.com/wp-content/uploads/82844.image4.jpg)
To apply the bead of caulk, move the caulk gun at a measured pace along the crack and using continuous light pressure on the gun trigger.
Smooth the caulk.
![Smooth the caulk.](https://www.dummies.com/wp-content/uploads/82846.image6.jpg)
You can use a craft stick, plastic spoon, or wet finger to create a smooth surface.
Caulk the remaining cracks following the same procedure.
![Caulk the remaining cracks following the same procedure.](https://www.dummies.com/wp-content/uploads/82848.image8.jpg)
Caulk on all cracks between gutter pieces.
Clean the caulk tube.
![Clean the caulk tube.](https://www.dummies.com/wp-content/uploads/82850.image10.jpg)
Wash away any caulk remaining on the gun, your hands, or other unwanted places before it dries.