Grade Rings – Frames – Covers for Fiberglass Manholes

One of the greatest benefits of Openchannelflow's fiberglass manholes is corrosion resistance. In a traffic loading configuration, a grade ring / frame / cover set is still required to bring the manhole up to grade. Made out of traditional materials, these items are still susceptible to corrosion.

For a true metal / concrete free installation, Openchannelflow’s customers have used composite frames / covers and HDPE grade (riser) rings.

Customers have used GMI Composites’ (now a part of East Jordan) 3200 series of covers / frames to fit Openchannelflow’s standard 31 ¾-inch H-20 reducer openings. Their 3800 series of covers have also been used to fit OCF’s optional 38-inch reducer openings.

GMI Composites manhole cover and frame

The standard height of the 3200 series covers is 5-inches – allowing for up to 7-inches of grade rings to bring the installation up to street level (remember that Openchannelflow’s traffic manholes are sized to be a foot below grade to allow for the grade rings / frame / cover to bring the installation up to grade). The cover is secured to the frame through the use of 1/4-turn camlocks. Optional cover gasketing is also available from EJ.

To bring the frame / cover system up to grade, Ladtech HDPE manhole risers / grade rings have been used. These risers are available in both round, fixed height and adjustable ring designs. Made of 100% recycled plastic, Ladtech risers do not rot or corrode as other grade ring materials might.

Ladtech HDPE manhole risers - grade rings