Gutter Sealant for Aluminum and PVC Joints

Mulco Gutter Waterproof Sealant is the direct fit in Cranco’s range for outdoor aluminum and PVC gutter joints. Its limits matter as much as its name.

Use Mulco Gutter Waterproof Sealant for an outdoor joint between aluminum or PVC gutter pieces. Prepare the material correctly, apply at least 3 mm (1/8 inch) thick and check the run-length limits before assuming the repair will be permanent.

This recommendation is specific to aluminum and PVC gutter joints. It is not a general sealant recommendation for roofs, tanks or submerged joints.

The direct answer

Mulco Gutter Waterproof Sealant is formulated for sealing outdoor PVC and aluminum gutter joints. The manufacturer says it remains flexible and adheres to dry or damp surfaces.

Do not use that as permission to seal over old material, frost, oil or loose contamination. The joint still needs proper preparation.

Prepare aluminum and PVC differently

  • Remove old sealant or putty, frost, ice, rust and loose material.
  • For new metal and solvent-resistant oily surfaces, the sheet calls for acetone cleaning followed by drying.
  • For vinyl or dirty plastic, wash with soapy water, rinse and dry.
  • Do not use a solvent on plastic unless the material is known to tolerate it.

Apply at least a 3 mm seal

  • Cut the nozzle at 90 degrees, slightly narrower than the joint.
  • Pierce the seal inside the nozzle.
  • Apply with even gun pressure over the joint and onto both sides.
  • Flatten the sealant and leave at least 3 mm (1/8 inch) finished thickness.
  • Keep the product above 5°C (40°F) during application and provide ventilation.

Drying time varies with temperature, relative humidity and ventilation. The sheet does not give one universal dry-time number.

Know when this repair is not permanent

  • Do not use it where the sealant will be immersed or exposed to abrasion or foot traffic.
  • Aluminum gutters longer than 20 feet cannot be sealed permanently with this product.
  • Vinyl gutters longer than 10 feet cannot be sealed permanently with this product.
  • Keep it away from flames, sparks and intense heat during application because it contains flammable solvents.

Confirm the material and run length

Identify whether the gutter is aluminum or PVC, measure the run and inspect the joint. If the material or exposure is different, ask before substituting another sealant.

Gutter sealant questions

What sealant should I use on an aluminum gutter joint? Mulco Gutter Waterproof Sealant is formulated for outdoor aluminum and PVC gutter joints.

Can I apply it to a damp gutter? The sheet says it adheres to dry or damp surfaces, but the joint still must be free of frost, ice, old sealant, oil and loose material.

How thick should the finished seal be? Mulco specifies at least 3 mm (1/8 inch) after the sealant is flattened over the joint and both sides.

Can it permanently seal a long gutter run? The sheet says aluminum gutters longer than 20 feet and vinyl gutters longer than 10 feet cannot be sealed permanently with this product.