Is Composting Toilets Legal in Hawaii? (2026)
Partially — Composting Toilets are legal with restrictions in Hawaii as of 2026.
Quick Answer
Composting toilets may be used in Hawaii but typically only as a supplemental system alongside a conventional toilet. While legislation has been introduced to mandate county approval of composting toilets, the specific rules and enforcement are still determined at the county level.
What the Law Says
Allows use of composting toilets as supplemental systems alongside conventional toilets, requiring county health department approval and adherence to local plumbing codes; unauthorized installation may result in code violations.
— Haw. Rev. Stat. § 27-21.6
| Category | Details |
|---|---|
| State Plumbing Code | May require conventional toilet as primary; composting as supplemental |
| Permit Requirements | Legal to sell |
| Code Violation Penalties | Installation without permits may result in code violations. |
| Pending Legislation | None known |
While legislation has been introduced to mandate county approval of composting toilets, the specific rules and enforcement are still determined at the county level. No major statewide changes have been enacted since the administrative rules were last updated.
Enforcement Reality
Enforcement is handled by the counties, which are mandated to approve composting toilets in areas without municipal wastewater systems. An engineer's design is often required for legal installation.
A common mistake is installing a non-approved composting toilet without a permit. Another is failing to have a system for greywater, as composting toilets only handle toilet waste.
Local Exceptions
None identified. State law applies uniformly across Hawaii. Local ordinances may still vary — check with your city or county government for any additional rules.
Bottom Line
Composting Toilets are legal with restrictions in Hawaii. This activity is permitted, but specific conditions apply. Violating those conditions can result in fines or criminal charges. Read the rules carefully and consult an attorney if unsure.
Hawaii vs. the Rest of the US
Across the US, installing a composting toilet is fully legal in 20 states, restricted in 30, and illegal in 0. Hawaii falls in the RESTRICTED category.
View the full 50-state map →Frequently Asked Questions
Is installing a composting toilet legal in Hawaii?
What are the restrictions on installing a composting toilet in Hawaii?
What mistakes do people make with installing a composting toilet in Hawaii?
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Reviewed by cross-referencing the cited state statute against current legislative databases and regulatory publications.
Sources & Verification
This page was reviewed by Ethan Harper by comparing the legal status against the cited state statute. AllowedHere is an informational resource and does not provide legal advice. Consult a licensed attorney for guidance specific to your situation.
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