Low flow velocity meter in a sewer pipe


Thread Starter


The meter cannot be permanently installed for security reasons. The water level in the sewer is about an inch at the lowest flow. There can be no entry into the manhole either because of confined space entry issues. I've already investigated the Global FP series and the diameter of the probe head is too large to be fully submerged. It has also received poor reviews concerning craftsmanship/mechanical failures/etc.

Any input into resolving this issue is appreciated. Thanks!
You will have to enter the manhole, or use a remote placement tool.

What is the diameter of the line and the depth of the manhole?

Is there surcharge and/or reverse flow?

Assuming the line diameter is less than about 10" and the depth of the manhole is reasonable-- 6 feet or so from street level to invert-- AND the line doesn't surcharge--- you can use an insertion Palmer Bowlus flume with a pressure transducer built in, and a battery operated data logger.

There are a number of companies that build them.

If the line is larger than about 10" OR the line surcharges you will have to use an area/velocity meter. If the line is 15" or smaller, you could use a Datagator, which is produced by Renaissance Instruments in Austin TX.

Several companies build area/velocity meters.

One approach is to hire a flow consultant who will do the flow study for you, with their own equipment and deliver you a report over whatever time base you need. Again, there are numerous consulting engineers who do this.

Good luck,


Walt Boyes, FInstMC, Chartered Measurement and Control Technologist
Life Fellow, International Society of Automation
Editor in Chief, Control and ControlGlobal.com
[email protected]