Overestimating Water Demands is Contributing to Rising Cost of Housing

By Eric Armstrong, Fuscoe Engineering, BIA Board of Directors
The Building industry has done a good job in adopting water conservation into their new homes. KB Home said it has built an “industry-record number” of WaterSense labeled and Water Smart-certified homes, estimating that those homes conserve 1.4 billion gallons of water annually. But as our local Water Districts update their master plans and capital improvement plans, we need to advocate for responsible water use forecasting that acknowledges the sea change in both indoor and outdoor water use. The consequences of not getting involved are oversized water and wastewater systems paid for by new home buyers through connection fees.


Engineers and Planners working for local water districts have routinely overestimated water demands resulting in oversizing of facilities. This is not because of some evil plan by the Water Districts to corner the water market and then jack up fees. They are following the recipe handed down to them by now retired General Managers who honed their water planning practices in an era when water was relatively plentiful and the main problem to solve was how to get the water from the source (the Central Valley and Colorado River) to the arid places where it was needed. This approach has served San Diego well because as our population grew and the demand for water increased, supply was available due to conservative planning.

Today in San Diego County, growth from in-migration has moderated and we are primarily building new homes for our children and our children’s children. And the way water is being used and reused is changing the conventional wisdom on how to project future demands. According to the most recent data compiled by the United States Geological Survey, water use, measured in gallons per capita per day (GPCPD), declined to 82 gpcpd in 2015 from 88 gpcpd in 2010. More conservation is coming due to advances in plumbing technology, gray water recycling systems, and surprising willingness of private citizens to conserve water when made aware of the scarcity of our most precious resource.

Current water planning does not factor in the water conservation regulatory measures enacted since 2006. These regulatory measures include SBX7-7, the CALGreen building standards, and the California Model Water Efficient Landscaping Ordinance (MWELO). Even the 2016 plumbing code used in California does not take into account high efficiency plumbing fixtures (HEPF) that have been in use for the past 10 years. The fact is water use will continue to decline on a per capita basis.