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Transcript
Using Water Wisely:
The Non-Potable Water Program
The Non-Potable Water Program creates a streamlined process for new large developments in San Francisco to
collect, treat, and reuse water for toilet flushing, irrigation and other non-potable uses. Established through an
ordinance adopted by the San Francisco Board of Supervisors, this voluntary program would establish guidelines
for developers interested in installing non-potable water systems and put in place local regulations that ensure
appropriate water quality standards.
Context
The City and County of San Francisco has long been a leader in water conservation and expanding local water
supplies to protect against droughts and the effects of climate change. In a dense, urban center like San
Francisco, the capture and reuse of water generated on-site—from graywater (sinks, washers, and showers),
rainwater, blackwater (graywater and toilets), and foundation drainage (water that floods basements)—is a key
strategy for expanding water savings and diversifying our water supply.
On-site water treatment and reuse is being implemented in
New York City, Portland, Seattle, and Sydney as a cutting
edge green building strategy. Tokyo mandates it. Recognizing
the environmental benefits and water savings that accrue,
the Transbay Transit Center and the new SFPUC
headquarters at 525 Golden Gate Avenue will be using onsite treated water for toilet flushing.
What is Non-potable Water?
Non-potable is a term that refers to water
that is not of drinking water quality but can
be used for other productive uses such as
toilet flushing and irrigation, in compliance
with applicable City, State and Federal laws.
Non-potable water is used across the nation
to reduce the pressure on natural water
resources.
The water savings that can be achieved in existing buildings is
limited due to plumbing retrofit requirements. Installing dual-plumbing at the time of construction—so that one
set of pipes delivers drinking water, and another set handles the non-potable water for toilets and irrigation—is
necessary so that San Francisco can facilitate widespread non-potable water use now and into the future.
Currently, San Francisco doesn’t have regulations in place to define a clear pathway for new developments to
collect and use their water. This hinders the wide spread installation of on-site treatment systems. By
establishing the Non-Potable Water Program, developers would know the necessary steps to collect, treat and
use water for toilet flushing and irrigation within new large scale developments and the city would establish
water quality standards to protect the public health.
The Benefits—Reducing San Francisco’s Water Footprint
o
Promoting Citywide Water Conservation. Capturing and treating rainwater, foundation drainage, and
graywater—and then reusing the water for toilet flushing and irrigation—would result in a dramatic
reduction in the overall water footprint of a building. This helps San Francisco save our pristine drinking
water for drinking purposes.
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o
Reducing a Building’s Water Consumption. Approximately 35% of a building’s total water use is from
toilet flushing with an additional 5% for irrigation. Implementation of on-site water use would result in a
considerable decrease in a building’s water and sewer bill.
o
Reducing Pressure on the City’s Sewer Infrastructure. Using captured rainwater and graywater reduces
the volume of flows into the sewer. Reducing the volume of stormwater, especially during the rainy
season, can prevent flooding.
o
Continuing San Francisco’s Leadership in Green Building Policy. On-site water reuse to meet toilet
flushing and irrigation demands is a recognized strategy under LEED, and can help developers get the
credits they need to certify their buildings. On-site water reuse also allows San Francisco to expand
water savings achieved under the City’s Green Building Ordinance, which was awarded the World Green
Building Council’s Government Leadership Award in 2011.
Key Ordinance Components
o
A Streamlined Process for Participating Developers. The Non-potable Water Program would direct the
San Francisco Department of Public Health (SFDPH) to establish water quality standards and monitoring
criteria for on-site systems. It would also direct the San Francisco Department of Building Inspection
(SFDBI) to issue plumbing permits for on-site systems to capture, treat, and reuse water on-site in new
commercial, mixed-use, and multi-family residential developments.
o
A Clear Pathway for Developers. Developers proposing to collect, treat and use water on-site would
need to: 1) inform SFPUC of potable and non-potable demands; 2) submit an Engineering Report
describing the collection and treatment on-site system to SFDPH; 3) obtain a Plumbing Permit from
SFDBI; and 4) obtain a permit to operate from the SFDPH.
o
Eligible Types of Water. Several water sources would be applicable for on-site reuse as part of the
proposed program, including rainwater, graywater, foundation drainage, and blackwater as approved by
SFDPH.
o
Eligible Uses for Non-potable Water. Water collected and treated on-site could be used for toilet/urinal
flushing, irrigation, and other uses as approved by SFDPH.
Tools to Support Successful Implementation
o
Water Use Calculator. The SFPUC has developed a “water use” calculator that developers can utilize to
estimate a building’s supply and demand for water. The profile would show the available supply of onsite graywater, rainwater, blackwater, and foundation drainage as well as the total water demand for
toilet flushing and irrigation. The developer would then have the information needed to design an onsite water use system that is uniquely tailored to meet non-potable water reuse requirements.
o
Efficacy and Reporting. The SFPUC would track all developments participating in the Non-potable Water
Program and issue an annual report that summarizes the “water offset” achieved and lessons learned
through the implementation process.
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