Marathon Roofing Products Inc.
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Roof Drains, Vents, Accessories And Pedestal Supports

Premium Large Capacity heat weldable PVC Roof Vent for pressure/moisture relief of roof systems. Available in one way or two way that meets 1-150 or 1 - 300 National Venting Code in combination with inlet vents.

Pre-Vent design provides venting capacity to accommodate 327 sq feet of floor. The Pre-Vent is UV Stabilized to help reduce any deterioration and fading from the sun.

To install the Pre-Vent properly it has been designed with pre- drilled holes in the flange to attach the Pre-Vent to the deck. The Pre-Vent when used with mechanical venting should be insulated accordingly to assist in directing the release of internal condensation. The base of the penetration within the Pre-Vent should be sealed to maintain the integrity of the roofing system. See your membrane manufacturers for details.

Venting capacity will be maintained through pipe sizes up to 80% of the diameter of the Pre-Vent.

Caps must be adhered to base with PVC glue.


  • Super heavy duty PVC plastic for long life
  • Exclusive one-way valve design to prevent moisture from re-entering the roof system
  • Special insect resistant wire screen
  • Vandal proof
  • Pre-drilled flange for fastening to roof deck


  • Available in one-way or two-way

Prevent Product Brochure

Prevent Data Sheet

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