How Does the FMD Actually Work?

ZennValve - overview-H2minusO

The Flow Management Device (FMD) is designed with three main functions to help clients reduce water consumption that is metered entering your facility.

  1. The FMD manages the flow from turbulent to uniform flow in the water line
  2. The FMD manages the size of any air (pockets, eddies, bubbles) in the water line
  3. The FMD manages the flow efficiency and flow rate traveling through the water line
  1. Turbulent Flow to Uniform Flow

Throughout the water distribution system there are many factors than produce turbulence in the line. From the pumping and lift station pumps, elevation changes, every tee, elbow, gate valve and pipe size transition there is opportunity for turbulence to be produced. With the oscillation of the valve piston at a given frequency we are increasing the effect and efficiency of the boundary layer in the pipe thus providing a turbulent/uniform transition zone prior to entering the water meter. This is further amplified through the utilization of Venturis’ principal being designed into the entry and exit of the flow through the FMD further providing linear stability.

  1. Where does the air go?

Air enters into the municipal distribution lines in a number of ways. Construction, repairs, elevation changes, cavitation….this air is delivered over a flow meter that registers both the air and water with no way to differentiate, thus inflating the reading of actual water used. The installation of the FMD takes these volumes of air entrained in the line and renders them unreadable by reducing the size of the pass through volume of air and dissipating into many smaller unreadable volumes. The air remains in the line. It still passes over the meter, but in a state that is undetectable by every water meter currently used by municipalities in residential, commercial and industrial applications.

  1. Managing Flow Efficiency

The orifice diameter for the plunger head is sized based on providing the most efficient flow for the installed location. The standard orifice size associated with each FMD size provides an actual water usage reduction. For facilities that require specific gallons per minute the FMD is custom manufactured to specific specifications.

General Overview of the FMD Operation

  1. The FMD works by combining the effects of the three design principles via Oscillation and Hydraulic Intensification.
  2. The FMD is installed with the plunger facing into the flow of water. The water flow is what powers the oscillation of the spring loaded plunger. The plunger arm then oscillates approximately 300 to 500 per minute creating the Transitional Zone 30 to 60 feet in front of the water meter “city side”.
  3. The FMD is installed as close the water meter as possible on the customer side of the meter. We discourage installing any further than 10ft from the water meter (although we have a few successful installs beyond 10ft.).
  4. FMD’s 2” and smaller are installed in-line. FMD’s 3” and larger have slip flanges and are installed inside the pipe.

The Technology Behind the Savings

The FMD is a self-perpetuated device that is activated by the pressure of the incoming water in the line. The FMD has a plunger head that oscillates between 300-500 times a minute, resulting in a hydraulic intensification upstream of the device. The result of hydraulic intensification creates a more uniform flow thru the meter. This hydraulic intensification creates a compression zone upstream of the meter reducing air pockets, eddies, or swirls that passes thru the meter resulting in higher consumption reading.

The spring which controls the oscillating plunger head is engineered specifically to the pipe configuration and water pressure of each specific location. The spring which is made of surgical stainless steel (316) is designed with several crack points to accommodate fluctuating water pressure. The angle of the holes cut into the stainless steel back plate as well as the angle of the plunger head and inlet opening creates a venturi effect across the FMD. This venturi effect allows for a nominal pressure loss (1-3 lbs) to the customer. The FMD is designed in a manner that if it were to fail, it would do so in the open position causing no disruption to the customer.

Guaranteed Savings

Savings Guarantee/Verification: The FMD comes with a 5% Savings Guarantee in billable consumption over the first 90 days. If the FMD does not save at least 5% in billable consumption we will remove the FMD and refund all cost associated with the product purchase and install. We will require monthly water bills for our savings verification chart.

Typical Savings

Depending on the facility we typically see the following savings:

Condo’s, Campus Housing, Mobile Home Parks, etc. 12% to 18% and as high as 35%

Manufacturing, Industry, large users, etc. 8% – 12% and as high as 20%

Office buildings, light industrial, etc. 10% – 15% and as high as 20%

Irrigation systems 10 % – 20% and as has as 40+%

**The FMD is designed to fail in the open position so as to never cut off water flow.


The FMD comes with a 10 Year Part Warranty and 1 Year Labor Warranty. Zennergy will either fix or replace any mechanical defects.

The 10 year warranty covers any mechanical defect from the manufacturing facility, while the 1 year labor warranty covers any plumbing fixtures and/or work used to install the FMD.

Pre-Site Analysis Process

This step is to determine if a site is a candidate for an FMD.

  1. Receive one year of historical water bills from the utility department
  2. Obtain the size of the water meter
  3. Zennergy provides a preliminary report of estimated costs and potential ROI
  4. Provide cost of On-Site Analysis facility visit

On-site Site Analysis (fee based)

A properly completed site evaluation will allow Zennergy and the manufacturer to calibrate the FMD to the specific needs of each location.   During this analysis, the following information will be evaluated:

  • Coordination with licensed plumber during on-site visit to obtain quote
  • Pressure readings before and after the backflow assembly
  • Static and Dynamic PSI
  • Size of water meter
  • Water meter number
  • Size of pipe on property side of meter
  • Pictures of water meter and all piping connected to and downstream of meter
  • Presence of Booster pumps, Cooling tower, Production equipment, etc. (including photos)