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State-approved vs. Site-built Composting Toilet in Birch House

Whatcom County, WA, USA

Building Type




Lee Phipps | Whatcom County Health
Jim Tinner | City of Bellingham

Dan Welch | Designer
Lee Phipps | approving-official
Jim Tinner | approving-official

To design and build his home to meet the Net-Zero Water imperative of the Living Building Challenge, architectural designer Dan Welch installed waterless composting toilets in his family’s home, and recycles their biosolids on-site “for beneficial purposes” in a manner approved by Whatcom County Health Dept. and City of Bellingham under State of Washington rules.  Although he argued those rules prefer a two-stage “batch composter” for improved sanitation, the County health official required him to choose a continuous composter from the State approved list, rather than his own site-built design.

The Birch Case Study Home uses several integrated systems to achieve Net-Zero Water, including rainwater harvesting for potable use, on-site infiltration of all greywater and stormwater, and composting toilets.  Before finally being approved to use a self-contained proprietary composting toilet model, [bundle] proposed two innovative urine diverting batch composting toilet systems to treat human waste on-site, but both were rejected by Whatcom Health Department.  One was a proprietary design from Sweden not on the state approved list, the second was a similar site-built system Welch designed himself.  Both proposed “batch” systems use removable 5 gallon composting chambers, with waste combined into two 90-gallon “primary composting” tote containers kept in a lockable accessory shed, where the excrement ages for 1.5 – 3 years so it can be disposed of safely.  Welch argued their design was best way to compost human waste in a residential setting and satisfy Section 4.4.7 of the WA DOH On-Site Wastewater rules which state “Means must be provided to keep separate waste undergoing treatment from finished end products.”

In the end they were forced to accept one of the proprietary models off the State approved list.  Ironically, they pointed out, all the systems on the state approved list are “continuous” composters which run the risk of releasing partially composted waste when “finished” compost is removed.

Code Requirement Compliance Path
Whatcom County Code Chapter 24.05 adopts by reference WA Administrative Code WAC 246-272A, which authorizes WA State Department of Health to set rules for the performance, application, installation and design of composting toilets. State rules do allow public domain site-built systems, but also say local code supersedes and allows.  WCC 24.05.090 allows only proprietary systems on State approved list Proposed site-built system conformed with Required Standards and Guidelines 337-016, Section A1(parts 1- (WA DOH), but County code required proprietary system listed in RS&G 337-024
Square Footage: 2065ft2

Separett Composting Toilet

Because [bundle] was striving to demonstrate the most effective and sanitary water management systems available in their case study house, they began their permitting efforts with a high-quality manufactured unit that was not on the state list. The model was the Separett, made in Sweden, designed to be used with two large tote containers that would allow compost to age for 1.5 – 3 years.  Separett toilets are certified to the ETL standard for hygiene and health care, but not to NSF 41 which is specifically required for approval and registration with the WA State Department of Health.

Next [bundle] designed a similar system that would be site-built instead of manufactured.  Their design, they argued, would be “the safest, most user-friendly way to successfully compost human excrement in a residential setting.”  The Washington State Department of Health has rules allow public domain, site built composting toilets without the need for NSF 41 testing, if the toilet is designed in accordance with specifications provided in the document RS&G 337-016, Subsection A1 Composting Toilets.  However, state rules say it is at the County’s discretion to make rules more or less stringent, and Whatcom County Health Department was unwilling to allow [bundle] to head down that approved pathway.

See related document “Site built composting toilet users manual.”  Keep in mind this design was NOT approved, and is provided for reference only.

To finally reach permit approval for the Composting Toilets, [bundle] had to choose a toilet off the DOH proprietary approved list. Composting toilets are found on Page 23. They chose to use the SunMar Excel AC unit. The Health department required two composting toilets. Whatcom DOH sets their rules to determine toilet capacity based upon the state guidelines.  They required two toilets for the household based on a calculation of 2 persons per bedroom. Thus for the Birch Case Study House, 3 bedrooms required capacity for 6 adults and thus 2 toilets.

The solid waste from the two SunMar units is treated in two composting toilets. Rather than a massive central composting unit connected to two toilets that requires its own room, self-contained toilets were used to demonstrate their suitability for both new construction and renovations. Waste from these toilets is composted with wood chips, aged for one year and distributed on site in forest lands.

The City of Bellingham was the permitting agency for plumbing approval in compliance with the Uniform Plumbing Code, with Bellingham amendments.

When using composting toilets, State rules allow for smaller on-site treatment systems and drain fields. All greywater waste from the [bundle] Birch Case Study House is treated in a small septic tank and infiltrated on site, scaled down to reflect the fact that no blackwater is produced. Sources of waste water include all showers, sinks, laundry and dishes, but not toilets.

Their goal was to develop a project as close to the Living Building Challenge as possible and achieve not only net-zero water but also net-zero energy, and use local sustainable materials throughout the house.  They co-hosted workshops with local environmental group Sustainable Connections to demonstrate the advanced systems and green materials to local builders, at different stages in the construction process.  They partnered with Northwest Energy Efficiency Alliance (NEEA) and Washington State University Cooperative Energy Program to field test an innovative heat pump water heater that uses CO2 as a refrigerant.  The manufacturer Sanden was in the process of obtaining UL listing so this unit can be sold in the US.  See related case study on Birch Home’s Water Heating / Radiant Heat Combotechnology!

Instead of spending thousands on permits and utility construction hookups for City Water and Sewer, Welch was able to invest that money in cisterns, water purifiers, a small septic tank for greywater, and composting toilets (read case study about Birch House public domain, site built composting toilets) taking Net-zero water to (almost) its logical conclusion.  Now his family enjoys purified rainwater for all uses including drinking, showers, laundry (but not toilet flushing), and lives the satisfaction of knowing their home has gone beyond sustainability to achieve a net-positive impact on the local and global environment.

Among other things, this project shows that when local municipalities and state regulators put innovative codes, policies and guidelines in place, regulatory barriers are largely eliminated. This makes it easier for innovative projects pursuing rigorous green building standards to obtain necessary permits and proceed to construction in a cost-effective and efficient way.  On the other hand, because they wanted to use their own site-built composting toilet, their journey to finally get their toilets approved took about nine months and delayed the project.  Welch concluded:  “In the end, we lost this battle and were forced to use a technology that we do not believe works well to protect the health of the occupants and public. The toilets do ‘work’ but are good examples of very poor design in numerous areas.

Dan Welch


Lee Phipps
Environmental Health Specialist


Jim Tinner
Building Official