Water Demand Trends in the Multifamily Housing Sector

About 25% percent of housing (or about 33 million residences) in the U.S classified as multifamily housing. In several areas of the country, the share of multifamily dwellings in the residential sector is increasing and in some dense urban areas multifamily housing is already the dominant residential sector.

Understanding underlying factors that influence multifamily water use patterns is increasingly important for water demand forecasting, water efficiency program development, and planning for future water supply needs. Relative to water use in the single-family sector, there is a knowledge gap concerning water use in the multifamily sector. This paper will provide results from research being undertaken as part of Water Research Foundation Project 4554, which seeks to develop and recommend sound and practical strategies for estimating multifamily water use for the purposes of water demand planning and management.

This paper will characterize multifamily water use trends among multiple water utilities. In doing so, the discussion will:

• Identify data sources and collection methods for classification and other criteria needed to characterize the multifamily housing sector
• Describe and compare various water use metrics, and associated variability and trends in primary sub-categories of multi-family housing
• Compare and contrast water use in the multi-family and single-family sectors, addressing proper use and interchangeability of metrics and benchmarks
• Demonstrate the use of geographical data to explore reasons underlying variability in water use
• Evaluate the impacts of plumbing fixture standards and water efficient plumbing technology

Finally, the paper will review models of water use derived from a large sample of multifamily properties nation-wide using a property-level database available from the Multifamily Market Research Energy and Water Survey available from the Fannie Mae. The models will provide estimates of the effects of multiple explanatory factors on multifamily use, including prices, climate, and other property and facility management attributes.