Manhole Flow Monitoring with Flumes

While Packaged Metering Manholes provide a turnkey, drop-in-place solution to below grade flow monitoring, not every budget can bear the cost. Many times, flow measurement has to take place in an existing manhole. However, using an existing manhole means that there are fewer flumes that can be used, as all of the flume / end connections must fit inside the manhole barrel.

Palmer Bowlus Flumes

Palmer Bowlus flumes can be a good fit for existing manholes as they can be quite compact and certain configurations can install partly in the downstream pipe - reducing the length of the flume in the manhole proper.

4-inch - 10-inch Palmer Bowlus flumes: 48-inch manhole
12-inch Palmer Bowlus: 48-inch manhole with shortened approach length
15-inch Palmer Bowlus: 60-inch manhole
18-inch Palmer Bowlus: 72-inch manhole with shortened approach
21-inch - 24-inch Palmer Bowlus: 96-inch manhole with shortened approach sections

Palmer Bowlus flume in an existing brick manhole

Unless the manhole is 60-inches or larger, it can be difficult to fit HS / H flumes in an existing manhole. The need for an approach section - even a shortened 3D one - means that the flumes can quickly become too long to fit.

Parshall Flumes

For standard Parshall flumes, the normal end adapters make the flumes longer than what can be accommodated in most manholes. This is not to say, however, that Parshall flumes can't be used - just that they are restricted to some of the smaller flume sizes.

One way the Parshall flumes can be adapted to be used in existing manholes is through the use of staged (or curved) end adapters. Here the end adapter is curved to fit flush up against the manhole wall. This eliminates the need to form transitions into / out of the flume and also shortens the flume so that it will fit in the manhole.

1-inch Parshall: 48-inch manhole with staged end adapters
2-inch Parshall: 48-inch manhole with staged end adapters
3-inch Parshall: 48-inch manhole with staged end adapters
6-inch Parshall: 72-inch manhole with staged end adapters
9-inch Parshall: 96-inch manhole with staged end adapters

Parshall flume with staged end adapters for installation in an existing manhole

Trapezoidal Flumes

Like the Parshall flume, Trapezoidal flumes are generally restricted to smaller sizes. Also, like the Parshall flume, Trapezoidal most easily install in existing manhole though he use of staged end adapters.

Small 60 Degree Trapezoidal: 48-inch manhole with staged end adapters or shortened pipe stubs
Large 60 Degree Trapezoidal: 48-inch manhole with staged end adapters
Extra Large 60 Degree Trapezoidal: 60-inch manhole with staged end adapters

Trapezoidal flume with staged end adapters test fitted to a manhole section