For various reasons of practicality and economics, many apartment buildings and strip malls receive water through one “master” meter. This removes the accountability of water use from the tenants, which have the most control over water use efficiency. As with all metering, metered customers usually use 15% to 20% less water than un-metered customers. Recently, efforts to submeter these facilities have been initiated by water agencies, building owners, and private entrepreneurs. State and local laws sometimes hinder these efforts, but many states have already introduced or enacted legislation to accommodate this need.
The greatest hindrance in implementing submetering is the plumbing system design and costs. Accurate or “true” submetering requires each unit or apartment be supplied by a single pipe source of water. Traditionally, multi-unit buildings were plumbed by sector, to minimize the quantity of pipe and installation costs. These plumbing sectors do not always correspond to rental spaces, especially in multi-story buildings. Many new buildings are now being plumbed to easily accommodate true sub-metering.
Where true submetering is not possible, there are various strategies available to estimate each unit’s water use by placing flow sensors or end-use meters on the major water use appliances end uses, such as: water heaters, faucets, showers, and/or toilets, etc. After the end-use data is collected at a central location, each unit’s water use is estimated, and then adjusted to the master meter consumption records. States have different regulations regarding the use of practices of estimated submetering.
Submetering sometimes requires retrofits, operations and costs that are significantly different from the large water purveyor’s core business. Where multiple meters per apartment are required, water purveyors generally avoid implementing the submetering itself. Private enterprise has accelerated submetering in areas where the water purveyor is reluctant to implement projects on master metered buildings. Water purveyors offering technical assistance and cost-sharing can greatly enhance the efforts and success of private companies and landlords implementing submetering.
To learn more about submetering and billing programs for multi-family housing download the following report:
Mayer, P. et. al. (2004) National Submetering and Allocation Billing Program Study
Submetering in Mobile Home Parks
In 2011 the state of Oregon updated submetering regulations related to manufactured housing to better encourage conservation and customer equity. This legislation is available for download below.
In 2000, the Santa Clara Valley Water District began a pilot program to provide water submeters to mobile home parks in order to assist them in conserving water. In 2002, the District equipped four large mobile home parks with submeters, replacing one-meter systems with submeters at each unit. A total of 754 submeters were installed through this program. Annual water savings for the four mobile home parks were estimated to be 15 to 30 percent. This reduction in water use was due to both changed habits caused by the pricing signal and to the discovery and repair of leaks. Details can be found in the downloadable report below.
Santa Clara Valley Water District (2007) Water Submetering in Mobile Home Parks
State regulations can also impede the advent of sub-metering. Some state regulations require water meters to be tested and calibrated for accuracy. Usually, this involves a sampling of meters tested each year, and each meter must be tested periodically, usually at least once per ten years. This is more easily accomplished by water purveyors, where the meters are installed outside of the apartment. Most sub-metering retrofits require the meters installed inside the home. Gaining access to these meters to perform testing can be very problematic. In addition, some state regulations require sub-metering purveyors to register as water utilities; this can be an arduous process and cost prohibitive for small sub-metering ventures.
NIST (2011) Submetering of Energy and Water
North County Times (2009) Renters May Get Water Bills in San Diego
CUWCC (2006) Potential Best Management Practices (PBMP) Report – Submetering