Sophisticated Submetering

Advances in submetering technology are stepping up results in water efficiency. 

Today’s most advanced two-way wireless mesh submetering systems are providing both visualization and control capabilities to property owners/managers and tenants. The biggest water savings from submetering often comes from the system’s ability to monitor and report data at individual toilets, showers, sinks, etc., throughout a multi-family building. Especially key is how this data is delivered to building managers in the form of daily email reports that enable them to identify and address problems. This monitoring/reporting capability is giving building managers the tool they need to eliminate a major culprit in unnecessary water consumption – water leaks.  

The graph in Figure 1 shows water consumption by point-of-use in apartments. Toilets account for 40 percent of the water usage, but more than 70 percent of the leaks. It is critical for property managers and tenants to identify and control leaks, mainly from toilets and, secondarily, from showers.  Submetering systems can now identify and report leaks by point of usage. 

Evolution of submetering technology

The type of sophisticated submetering system described in this article uses a comprehensive approach that employs a combination of two-way wireless mesh technology, water meters, “smart” green thermostats and daily water meter usage and leak-detection reporting. Low-cost, compact water submeters provide flexible metering options to monitor usage for an entire apartment or individual points of use such as a toilet as pictured in Figure 2. These meters can monitor up to 8 gpm at an extremely high accuracy rate, +/- 1 percent, which meets and or exceeds current AWWA accuracy standards.  

When submetering an apartment, the actual plumbing design will determine the number of water meters required. Based on the design, each building is different, as shown in Table 1. 

Wireless mesh radios are used by submetering companies to communicate with the water submeters, monitor data and transmit the information for usage, billing and leak detection reporting. Wireless mesh refers to wireless radio protocol documented in the IEEE Standard 802.15.4. As such, any product that uses this protocol to communicate can send its data over any wireless mesh network, or WMN. It is actively supported by 175 companies, including Cisco, Motorola, IBM, Samsung and Johnson Controls, to name just a few.
An advanced submetering system using two-way wireless mesh facilitates easier and lower-cost installation. The self-configuring system’s battery-powered radios are integrated with the water submeters and report periodically throughout the day. The elimination of running hard wires for communication in a plumbing system is critical in lowering the installation cost. The building’s usage data by apartment is collected wirelessly and stored at a central point called a gateway. Once at the gateway, the data is transmitted over the internet to a cloud-based server for report generation. All of the wireless infrastructure and web-based reporting is fully automated and does not require any responsibility on behalf of the property manager other than taking advantage of the data and reports.

Application example

Cheverly Crossing, a 60-unit apartment building in Hyattsville, Maryland, installed an advanced monitoring and control system after realizing that their utility expenses were being heavily impacted by water usage. They chose H2O Degree’s comprehensive wireless mesh submetering system based on its ability to monitor water/sewer, electricity and gas usage. The system at Cheverly Crossing also includes a dedicated web portal that allows residents to access their hot water heating energy usage. The following application example focuses on the system’s unique water monitoring and leak-detection features.

The Cheverly Crossing property is a six-floor building with 60 apartment units. It has a riser-piped water system with a central gas boiler generating domestic hot water energy. In each apartment unit, the submetering system’s battery-powered wireless water meters are mounted at the tub, shower, toilet and the kitchen hot water feed. The four meters, per apartment, collect water consumption data from the flow sensor. The meters monitor for water usage in gallons and record the number of events, the duration of events, water temperature and heat.

At Cheverly Crossing, the thermostat and electric meters act as transceivers. The battery-powered water meters communicate with a transceiver. This advanced wireless network results in substantial savings over traditional wireless repeater networks. 

The diagram in Figure 3 shows how the comprehensive metering system is installed throughout the Cheverly Crossing apartment building. As illustrated by the green line in the diagram, wireless water meters “talk” directly to any wireless mesh transceiver that responds to a signal. The wireless transceivers, thermostats or electric meters act as a transceiver and a transmitter, sending data from one device to another. Data is transmitted via the internet from the on-site gateway to submetering company’s cloud-based servers for access from any web-enabled location. 

It should be noted that battery-powered meters will only communicate with one transceiver at a time. This diagram represents a variety of transmission possibilities and will change depending on the building configuration and environmental changes since the wireless mesh network is self-healing.

Monitoring data

Once the submeters were installed at Cheverly Crossing building the utility data was collected at each tenant location. An essential calculation shown on the report is the average daily water consumption, or ADC, which is typically 70 gallons of water per day for a typical one-bedroom apartment. However, Cheverly Crossing’s ADC was a staggering 200 gallons per day.

The metering data collected by the submetering system was shared with the billing company, who then passed on the water bills to the tenants based on their individual usage. Simply by seeing the costs of their water usage on their bills, the tenants immediately changed their behavior by reducing their water consumption and making sure that toilets weren’t running. 

Leak detection

In addition to monitoring and recording water consumption for tenant billing, the wireless water meters installed at Cheverly Crossing also detected leaks. After the installation, the submetering data collected at each tenant location was used to create Leak Detection Reports that were delivered daily via email to the building’s landlord, so that maintenance staff could respond and make repairs before the leaks generated significant waste. By pinpointing water leaks in exact locations, building maintenance staff was immediately able to replace specific parts – flapper valves, stuck chains, cracked flow values, etc.

Submetering results

The landlord’s proactive maintenance, combined with the tenants’ water conservation, enabled Cheverly Crossing to bring its ADC from 200 to 80 gallons in the first year – and lowered it even more in subsequent years. 

The significant reduction in water use was mainly due to leak mitigation. In this case, the on-site manager was aggressive in repairing leaks as they were reported. Soon the property began reporting “0” leaks and maintaining water use in the range of 65-75 gallons per apartment, per day, for the total property (this figure includes water used in common area laundries.) 

The Cheverly Crossing apartment building installed its water submetering system in July 2009. The water/sewer rates provided by Cheverly’s water utility Washington suburban sanitary commission (WSSC) are graduated, so that high consumption is penalized with a much higher rate per thousand gallons. 

While Cheverly Crossing reduced water use by 66 percent in the last 12 months compared to the baseline in 2008, they reduced their water/sewer expense by over 80 percent. The building’s water/sewer averaged $115 per apartment per month in the first nine months of 2008 – in the first half of 2010 dropped to an impressively lower $13.25 average. In the first year after the submetering installation, Cheverly’s total water sewer expense went from $73,320 in 2008 down to a significantly lower $13,565 over the last 12 months of 2009. And since 2010, the results have been maintained at this low level (Figure 3).   

When the first year of submetering results from Cheverly Crossing were analyzed, the property owner showed a $70,000-plus per year cash flow improvement and a $1.32 million boost in property valuation ($22,000 a unit), as shown in Table 2.

Based on the initial energy savings, the property owner at Cheverly Crossing was able to implement a rent reduction for existing residents of around $170, which was most of the projected $223 average monthly cost of utilities. Since the installation at Cheverly Crossing, the property has been able to maintain the number of gallons used since 2012 at the same low rate, mainly thanks to ongoing reporting and proactive repairs.

Summary 

Advances in submetering offers new insight into water usage, that enables critical behavioral changes by both tenants and building managers that can dramatically increase water efficiency. Tenants can now view their individual water consumption on web portals, which prompts them to conserve. Property managers/owners are using monitoring data to better allocate water bills according to the tenants’ usage, enabling them to recoup utility costs and to incentivize tenants to further reduce consumption. But the biggest water savings is the result of the submetering systems’ capabilities for detecting and reporting leaks. 

Don Millstein is president of H2O Degree. A well-established industry professional, Don is a board member on the UMCA (Utility Management & Conservation Association). Don was president of E-Mon for 23 years before selling it to the Fortune 100 company, Honeywell. Prior to that, he held the positions of president of Encelium Technologies and senior auditor at KPMG U.S. Don has extensive business development and strategic sales experience in the following industry areas: electric metering, energy management software, HVAC controls, lighting controls and LED lighting.

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