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What’s a Packaged Metering Manhole?

The Packaged Metering Manhole was introduced to the wastewater market by Plasti-Fab, Inc. in 1982. In its simplest form it consists of a flume molded into a composite (FRP) manhole. The full range of flumes may be integrally molded into the composite manhole, along with inlet and outlet adapters, pipe stubs, and monitoring accessories for a complete package. Packaged Metering Manholes (PMMs) provide a complete and water tight flow monitoring package that can easily be installed during initial construction or as a retrofit when there is a need to measure flow in an underground sewer pipe without access to an existing manhole.

For installation on existing sewer lines an area at least the size of the manhole is excavated and the existing sewer line is cut to match the length of the pipe stubs on the manhole. A concrete pad is then poured or set in place to provide a level surface for the PMM and to act as an anchoring device to overcome buoyant forces acting on the manhole. The PMM is set on the pad, leveled with shims and anchored in place. The typical method of connecting the existing sewer pipe to the pipe stubs on the PMM is with neoprene boots which offer some flexibility and forgiveness in lining up the pipe to the pipe stubs. The area around the manhole is then backfilled and you are left with easily accessible flow monitoring package.

Plasti-Fab, Inc. PMMs interiors are finished with a premium grade marine white gel coat that provides a smooth non-porous surface to resist bacteria for a cleaner environment, and to maximize illumination for a safer workspace.

During installation, the void space on the sides of the flume are typically filled with sand and capped with grout with a slope back towards the flume. This allows all water to flow back into the flume and out the manhole in the event of a sewer backup.

Plasti-Fab, Inc. PMMs are built to meet the requirements of ANSI/ASTM D-3753 “Standard Specifications for Glass-Fiber-Reinforced Polyester Manholes and Wetwells.” Packaged Metering Manholes are available with:

  •  All flume types and sizes
  • Hinged lid or concentric manhole reducer with H-20 rated lids or non-traffic load manhole covers
  • FRP Ladder standard on 4’ and deeper manholes (exceeds OSHA Safety Standard 1910.27)
  • All standard flume accessories (i.e. sample pipe, bubble pipe, ultrasonic flow meter bracket, stilling wells, pH probe lift out brackets, etc.)
  • Safety rails, harness, and access poles
  • Air vents

In addition to flumes, Packaged Metering Manholes can be equipped with pipe connections for installing magnetic flow meters or other pressurized line type flow meters.

For more information on Packaged Metering Manholes contact your nearest representative.


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