Measuring Water Use with Flume

Although roughly eighty percent of the water extracted in California is used in agriculture, residential water use is still substantial, exceeding 4 billion gallons per day. The East Bay Municipal Utility District (EBMUD) provides its customers with an average of 170 million gallons per day (mgd)—140 mgd in winter and 220 mgd in mid-summer—and a bit less than two-thirds goes to residential customers.

Since the drought in the mid-1970s, California has been a leader in improving the efficiency of residential water use. In the past, a typical toilet used 3 to 7 gallons per flush; today, the standard is 1.3 gallons and there are toilets available that use two-thirds of that.  In 2016, the Water Research Foundation reported an average residential indoor use of 59 gallons per capita per day (gpcd), a 15% drop from results of a similar study in 1999. The 2016 report suggested that up-to-date appliances could drop the value to 37 gpcd. Employing appliances that have entered the market since 2016, EcoBlock hopes to lower the daily per capita usage of each participating household to 30 gallons or less.  

The Flume Smart Home Water Monitor systems that EcoBlock plans to install can detect flows as low as 0.01 to 0.03 gallons/minute—the company expects to have developed software that will help differentiate among various uses (toilet vs. shower vs dishwasher, etc.) this year.  Perhaps most importantly for EcoBlock residents: the Flume device will warn users if a leak develops. 

How does Flume work? 

The Flume system attaches to the outside of the residence’s EBMUD meter and utilizes the magnetic field generated by the meter to measure water flow. The EBMUD meter has two separate compartments: water passes through one compartment that contains a device (impeller, nutating disk, etc.), which passes a precise, fixed volume of water for each cycle of the device. This device is magnetically coupled to a disk in the recording compartment that completes a single rotation for each cycle of the device and transfers this information to the meter’s recorder. The Flume system also utilizes the meter’s oscillating magnetic field to record each cycle of the device and convert that to the volume of water passed through the meter.  

The Flume system involves two components: the flow monitoring unit that attaches to the utility water meter and the Wi-Fi bridge that communicates information from the Flume meter to the smartphone app. The Wi-Fi bridge requires 120V power (or a low power Direct Current source) then uses a different wireless method to reach the sensor on the water meter. The water flow detector runs on 4 AA batteries that are easily swapped out and whose charge level is monitored by the smartphone app. 

The EcoBlock team believes that its proposed water interventions will result in substantial water savings. Data from the Flume systems will show whether or not these beliefs are warranted and will assist in the development of future EcoBlocks. The Flume system will provide residents with a detailed breakdown of their water use, allowing them to make informed choices.