Things You'll Need
1/8 inch drill bit
abrasive rotary tool tip
Polyethylene welding rod
Polyethylene septic tanks, most commonly called plastic septic tanks, can last longer than their concrete counter parts. In rare circumstances, a crack can develop on the polyethylene septic tank, needing immediate repair. If the crack is not repaired, it can continue to grow, possibly making the tank unrepairable. Luckily, plastic-welding the septic tank will fix the crack and prevent the crack from growing. Depending on local building ordinances, you may be able to repair the tank yourself saving you hundreds of dollars.
Call a septic tank contractor to pump out your septic tank. Only a licensed septic tank contractor can pump a septic tank out. Do not attempt to pump a septic tank out yourself because it is illegal and can cause deadly gas to escape.
Clean the surface of the septic tank where the crack is located. Wipe it clean with a moist rag removing any dirt and debris in the crack.
Drill a small hole with the 1/8 inch drill bit at the top of the crack and the bottom of the crack. The small hole will prevent the crack from expanding.
Sand a groove along the crack with the rotary tool with an abrasive tip. Begin making the groove 1/2 inch above and beyond the crack. The grove will make a void in the crack, so the welding rod can fit inside the void, sealing the crack.
Cut the tip of the polyethylene welding rod with the utility knife, so it looks like a pointed pencil. Insert the welding rod into the plastic welding gun.
Place the tip of the welding rod at the top of the crack. Apply pressure on the welding gun as you pull the gun through the end of the crack. Read the instructions on your particular welding gun as it can vary significantly depending on manufacturer. Let the weld dry for at least an hour before covering the tank and using it again.