Quality Assurance & Quality Control
Introduction to Radon Mitigation
Worker Health & Safety
2 of 3

System Vent Piping

Vent Pipe Size

  • The main run of vent pipe, from primary suction point to exhaust is a minimum 3-inch in diameter (exteriorly 3-inch by 4-inch metal downspout may be used).
  • Vent pipe and fittings are Schedule 40 PVC, appear to be air tight and properly joined / sealed.
  • Vent pipes are supported every 6 feet on horizontal runs, every eight feet on vertical runs that do not penetrate floors, ceilings or roofs and supported at the floor.
  • Vent pipes are installed in a configuration that ensures that any rainwater or condensation drains downward into the ground beneath the slab or soil gas retarder membrane.
  • All vent stack, manifold, and suction point piping must be solid, rigid pipe no less than 3” inside diameter (ID).
  • The vent stack piping ID must be at least as large as the largest used in the manifold piping.
  • A minimum 4” manifold piping must be when connecting two or more suction points.
  • Contractors are advised to seek industrial ventilation guidance when installing 3 or more suction points.
  • Alternate pipe sizes may be used when sufficiently justified by field diagnostic measurements, including static pressure, air velocity, and rate of air flow measurements, and documented using the methodologies found in “Industrial Ventilation: A Manual of Standard Practice, 23rd Edition,” or its equivalent.
  • When alternate pipe sizes and shapes are used, a statement of justification must be provided to the building owner.  This justification must include methodology, calculations employed, and all site specific field data collected.

Vent Pipe Insulation, Joints, and Seams

  • All interior and exterior pipe joints and connections both must be sealed permanently. Exceptions:
    • Radon fans
    • Sump covers
    • Interior and exterior vent piping must be insulated where condensation on the pipe’s exterior may drip onto and damage ceilings and floors, etc., and where water vapor, from the soil, may condense inside the pipe, and then freeze partially or fully blocking the soil-gas exhaust.
  • Piping should be fastened to the structure of the building with hangers, strapping, or other supports that will secure it adequately and must not be attached to or supported by existing pipes, ducts, conduits, or any kind of equipment.

Vent Pipe Supports

  • Vent piping should be supported at least every 6’ on horizontal runs.
  • Vent piping should be supported at least every 6’ on vertical runs that do not penetrate floors, ceilings, or roofs.
  • Vent piping that penetrates floors, ceilings or roofs should be supported at the point of penetration.
  • To prevent blockage of air flow into the bottom of suction point pipes, vent pipes should be permanently secured to prevent downward movement of the pipe into the bottom of suction pits or sump pits, or into the soil beneath a soil-gas-retarder membrane.

Vent Pipe Discharge Point

To prevent blockage due to heavy snowfall, re-entrainment into the living spaces of a building, and to prevent direct exposure of individuals outside of buildings to high levels of radon, the discharge points must meet the following minimum requirements.

Vent Pipe Discharge points must be:

  • Vertical and upward
  • Outside the structure
  • Above the highest eave of the roof and as close to the roof ridge line as possible to prevent re-entrainment of radon or direct exposure of individuals outside the building to high levels of radon.
  • 10 feet or more above the ground level.
  • 10 feet or more from any window, door or other opening into conditioned spaces of the structure that is less than 2 feet below the exhaust point, including chimney flues.
  • 10 feet or more from any opening into an adjacent building.
  • The discharge point for vent pipes that penetrate the roof must be at least 12 in. above the surface of the roof.
  • The discharge point for attached to or penetrating the sides of buildings must be at least 6 in. above the edge of the roof and in such a position that it can neither be covered with snow, or other materials nor be filled with water from the roof or an overflowing gutter.
  • In areas where it snows the point of discharge point must be at least 12 in. above the surface of the roof.
  • Points of discharge that are not in a direct line of sight from openings into conditioned or otherwise occupiable space because of intervening objects, such as dormers, chimneys, windows around the corner, etc. should meet all other separation requirements.