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Composting Toilets at the Six-Story Bullitt Center

Case Study by Jeff Michael, Daniel Cherniske, Jelica Summerfield, Jeff Motto and Dejonee Roder
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Composting Toilets at the Six-Story Bullitt Center
Plumbing Systems
Composting Toilet
6-story building with Composting Toilets
City of Seattle
Nouri Samiee, Seattle Public Utilities
Dave Cantrell, Chief Plumbing Inspector, WA
The Bullitt Foundation
Miller Hull Partnership
PSF Mechanical
Point 32
Living Building Challenge Certified


The Bullitt Center is a unique, first-of-its kind office building in downtown Seattle at 1501 Madison Street. The building is designed to meet the rigorous standards of the Living Building Challenge (LBC), including Net Zero Energy and Net Zero Water. Working directly with the City of Seattle and their LBC pilot program, new technologies and design elements for sustainability were permitted or allowed through conditional-use permits, variances, and exclusive permissions from the city. Micro-foam-flush marine toilets with an onsite composting system are used to help achieve the Net Zero Water goal and adhere to the requirements of the city’s pilot program.

Permitting Process

2020 Engineering worked with Public Health Seattle King County (PHSKC) as well as the Seattle Plumbing Department to permit the composting toilets. Because the composters were entirely contained within the building, both the fixtures and the composters themselves were permitted through plumbing permits in accordance with the Universal Plumbing Code. The composters are National Sanitation Foundation (NSF/ANSI) certified and are approved for use in Washington state. It would have been much more difficult to permit a non-approved or non-proprietary system. Although it was not difficult in this case, permitting specific toilet fixtures can sometimes be an issue. Because typical composting systems vent air down through the toilet, through the composter, and out through an exhaust pipe, the toilets do not have a p-trap (a device that prevents the odorous gas in plumbing drains and sewers from rising up through the toilet). This, along with not installing a typical exhaust fan in the bathroom (since we want the air to come into the bathroom rather than out), can be problematic with plumbing and building departments. However the City of Seattle is more supportive of these types of alternative systems; they were open to our justification and allowed it.

Project Description

composters arrive

In 2009, a partnership between the City of Seattle and the International Living Building Institute created a pilot program for up to 12 Living Buildings to be permitted under a new city ordinance: SMC 23.40.060: “The purpose […] is to establish a Living Building Pilot Program. The goal of the Pilot Program is to encourage the development of buildings that meet the Living Building Challenge by allowing departures from code requirements that might otherwise discourage or prevent buildings from meeting this standard.” This ordinance means that special conditional-use permits or variances were either more easily obtained or allowed by the city.

One intention of the ordinance is to help Seattle code officials understand where current code creates barriers for green design. Code innovations uncovered during the pilot program will help shape future Seattle building codes. This means elements like the composting toilet system, which isn’t necessarily against current code, will have a clearer regulatory path for becoming a viable alternative to a traditional sewage system. The Living Building Challenge requires a project to meet twenty specific imperatives within seven performance areas (or “Petals”): site, water, energy, health, materials, equity and beauty. These are subdivided into twenty Imperatives, each of which focuses on a more specific building or design concept. The two Imperatives relating to this composting toilet system, Net Zero Water and Ecological Water Flow, read (respectively): “100% of occupants’ water use must come from captured precipitation or closed loop water systems that account for downstream ecosystem impacts and that are appropriately purified without the use of chemicals... 100% of storm water and building water discharge must be managed onsite to feed the project’s internal water demands or released onto adjacent sites for management through acceptable natural time-scale surface flow, groundwater recharge, agricultural use or adjacent building needs.”

This came into conflict with KCC 13.24.035, which necessitates a sewer utility hook-up within the urban growth boundary. Working with PHSKC, 2020 Engineering designed the building to be constructed with both a public sewer line and ten Phoenix R-200 composting units located in the basement. This adds to the overall cost, but is necessary if the composting system fails and as an additional public health safeguard. Micro-flush toilets use 3 ounces of Neponol, a type of foaming biodegradable alcohol, per flush. The composters require minimal maintenance: each unit needs to be “churned” one rotation per day,year. and add about 1 gallon of bulking agent (wood chips) per 100 uses, producing about 12 cubic feet of compost per week.

composters descend

Additional Resources

"Regulatory Pathways to Net-Zero Water:  Guidance for Innovative Water Projects in Seattle."  February 2011 by the International Living Future Institute.
"Optimizing Urban Ecosystem Services:  The Bullitt Center Case Study" by Stuart Cowan et al, Published June 1, 2014 by EcoTrust, Portland Oregon

Design / Build Process

The design example may be viewed on Bullitt's website:

Lessons Learned

To read further about the lessons learned, click

To read about the progress of Local Ordinances Related to the Living Building Challenge, read the Report Prepared by Cascadia Green Building Council for King County GreenTools

To understand how the Bullitt Center and The Bertschi School Living Science Wing overcame regulatory hurdles in the context of the Living Building Challenge, read the report Legal Hurdles Faced by Deep Green Buildings: Case Studies and Recommendations, O'Brien Kathleen et al.


For up to date information, please check the Bullitt Center's website:

Recent articles in the Seattle Daily Journal of Commerce:

Project Contacts
Designer: Brian Court Miller Hull Partnership Designer: Colleen Mitchell 2020 Engineering Approving Offcial: Dave Cantrell Seattle King County Health Department
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