Domed Tops for Fiberglass Metering Manholes in Non-Traffic Areas

The domed top style is the most popular style of top for fiberglass metering manholes - outselling both H-20 traffic reducer and aluminum top styles 2:1. The dome top is specifically formed to provide rigidity and strength while still being light enough for operators to open.

A domed top manhole is designed to stick about a foot above grade. This helps to not only keep surface water out of the manhole but also helps operators get into / out of the manhole - the lip of the manhole acting as a convenient handhold.

While strong - and field tested to withstand the weight of a car - domed manhole can’t be used in areas where vehicular traffic is present. If a domed top manhole is installed near where traffic is or may be present, it’s important to install bollards, posts, or some other means between the manhole and the traffic.

H-20 traffic manhole left - domed top maholes center and right

If pedestrian foot traffic is going to occur, it may be better to use an aluminum cover instead of a domed top as the top could be a trio hazard. Aluminum hatch manholes are designed to be flush with the surrounding grade (instead of sticking up). If a domed top manhole is used in a pedestrian area, the cover can be provided with in high visibility color or markings as a visual warning or the foot traffic can be directed around / away from the manhole.

open domed top manhole showing gas strut and hinge The lid of a domed top manhole is mounted to the manhole barrel with a stainless steel piano hinge which is attached to a stainless steel hinge block (which is itself bolted to the manhole barrel). The lid can be secured with a padlock using the stainless steel hasp / staple provided with the manhole.

To support the lid and keep it open when in use, a stainless steel gas strut is provided. The strut helps the operator to open the top, but is sized so that it doesn’t provide too much force (making the manhole difficult to close).

One thing to keep in mind: domed top manholes are not intended to be gas tight (nor watertight). The force of the gas strut may be such that the top crowns to a degree. If top must be gas or watertight, a custom aluminum cover must be used (as the standard aluminum cover is also not intended to be gas / watertight).