Cesspool Conversion in Hawaii: 2050 Deadline, Costs, Steps and Financing (2026)
Short answer: Every cesspool in Hawaii has to be replaced with a Department of Health (DOH) approved septic or aerobic system, or connected to a sewer, before January 1, 2050, and some homes must do it sooner. Plan on hiring a licensed civil engineer first, budgeting tens of thousands of dollars, and allowing several months. A new state loan program is coming but was not open yet when we checked.
Last updated October 20, 2026. This is general information from Hawaii Department of Health, state, county and news sources listed below. It is not legal or engineering advice. We are an independent referral service, not a contractor or engineer.
The deadline, and what can make it come sooner
Under HRS 342D-72, every existing cesspool must be upgraded to an individual wastewater system (IWS, meaning an approved septic tank or aerobic treatment unit system) or connected to a sewer before January 1, 2050, unless an exemption applies. DOH says a 2025 bill that would have moved higher-risk cesspools to a 2035 deadline (SB 542) did not pass, so 2050 still stands.
DOH lists these situations that require an upgrade before 2050 (HAR 11-62-06(m)):
- You propose a building change that may change the amount or kind of wastewater, such as adding a bedroom, bathroom or kitchen. On Kauai, the district health office also lists adding an ADU, changing the use from residential to commercial, and, where the cesspool discharges into groundwater, adding a carport, lanai or bathroom.
- The cesspool has caused illness, nuisance, odors or unsanitary conditions.
- It has been pumped more than twice in the last 12 months, or has spilled more than once.
- It discharges directly into the groundwater table.
Two homes sharing one cesspool, or a home also used for a business such as child care, can make it a "large capacity cesspool," which falls under federal EPA rules and was banned in 2005. DOH says violations of Hawaii's water pollution law can bring fines of up to $60,000 per offense, per day.
Do you actually have a cesspool?
DOH notes that people often call a cesspool a "septic system," or assume a home is sewered when it has its own system. Ways to find out:
- Request your property's records from the DOH Wastewater Branch (have your Tax Map Key, or TMK, number ready). Many older cesspools have no record because owners never called for the original inspection.
- Have a licensed plumber, wastewater engineer or certified operator inspect the property. A camera inspection of the main line can show where the waste goes.
- On Oahu, ask the City's Department of Planning and Permitting Wastewater Branch at (808) 768-8210 whether a sewer connection is available to your lot.
Your options
| Option | When it fits | What to know |
|---|---|---|
| Connect to a public sewer | A sewer line runs near your lot (more common on Oahu) | In Honolulu, a new connection from an unsewered lot needs a Sewer Capacity Analysis from DPP; you then pay monthly sewer fees. Ask about cost of the lateral to the street. |
| Septic tank plus absorption field | Most single-family homes without sewer | The most common IWS. The leach field is fragile: no slabs, sheds or tree roots on top. DOH recommends pumping every 3 to 5 years. |
| Aerobic treatment unit (ATU) | Sites near the shore, wells or streams, high groundwater or poor soil | Higher treatment level. DOH requires a certified operator and an active service contract, and components usually need replacing every 10 to 20 years. |
| Other DOH-approved systems | Specific site needs | DOH also lists passive aerobic systems that still use a septic tank, bioreactor gardens, and composting or incinerator toilets (these treat toilet waste only). |
Only a licensed engineer can tell you which option your lot allows. On Hawaii Island, where about 71% of households have no central sewer according to the 2021 state finance report, an onsite system is likely the only option for most owners.
What it costs
| Source | Estimate |
|---|---|
| Hawaii DOH finance report (2021, historical upgrades statewide) | About $9,000 to $60,000 or more |
| DOH Cesspool Conversion Working Group briefing | $10,000 low, $23,000 average, $38,000 high; plus about $33 to $108 a month to operate |
| Wastewater Alternatives and Innovations, quoted by Hawaii Public Radio (June 2026) | $25,000 to $50,000 |
| Hawaii County Cesspool Conversion Task Force (2025 report) | Median about $40,000, upper range about $70,000 on Hawaii Island |
The older figures are lower largely because they are older. DOH says most of the price is materials and construction, with the rest going to engineering. Ask each bidder to separate engineering, DOH and county permit fees, excavation, the tank or unit, the leach field, cesspool abandonment, and yard or driveway restoration. On Kauai, the district health office lists a $100 state plan review fee paid when the engineer submits plans.
The approval process, step by step
- Hire a Hawaii-licensed civil engineer. DOH publishes a list of engineers who prepare IWS plans, and you can confirm any engineer's license in the DCCA license search.
- Site work and design. The engineer surveys the property, runs a percolation test and sizes the system for your bedrooms and flow.
- DOH review. The engineer submits the application, owner's certification and site evaluation forms to the DOH Wastewater Branch (online at wastewater.ehawaii.gov). DOH says reviews have averaged about 10 days, and engineers have taken about 25 days on average to answer comments. DOH talks to your engineer, not to you, so ask your engineer for updates.
- Hire the right contractor. After approval, the system must be built by a contractor holding an A, C-9, C-37, C-37a or C-43 license. DOH will not accept work by a contractor with another license class. You may also need a licensed plumber or electrician.
- Construction. DOH says installation has averaged about 200 days. Your engineer should inspect before backfill.
- Approval to Use. The engineer submits the final construction inspection report and the contractor certification form. DOH then issues an Approval to Use. Without it, the new system is not in compliance, even if the county has signed off on your building permit.
Financing and grants (checked October 20, 2026)
- Statewide loans: HB 1618, signed July 8, 2026 as Act 204 according to the Legislature's measure page, created a Cesspool Conversion Revolving Loan Fund run by the Hawaii Green Infrastructure Authority (HGIA) for low-interest or forgivable loans. (The DOH page refers to the same program as Act 120.) Hawaii Public Radio reported $2 million in initial state funds plus $625,000 from the City and County of Honolulu, and said Oahu residents who apply before 2030 could qualify for zero-percent loans. HGIA said it planned to launch by the end of 2026. No application or final terms were posted when we checked.
- Kauai County: Round 2 of the Residential Cesspool Conversion Grant Program (50 reimbursement grants of $20,000) closed October 6, 2026; later applicants go on a waitlist. Contact housing@kauai.gov or (808) 241-4444.
- Ended programs: the 2023 $20,000 Cesspool Pilot Grant Program and the 2016 to 2020 $10,000 state tax credit are closed.
- Free help: Wastewater Alternatives and Innovations runs a "Potty Portal" with technical assistance for homeowners.
Island notes
- Oahu: More homes are near a sewer line, so ask about a connection first. Honolulu ENV lists a cesspool pumping service at (808) 768-7232 (weekdays 7:30 a.m. to 3 p.m.) and the sewer connection permit line at (808) 768-8210.
- Hawaii Island: The county task force counts roughly 49,000 cesspools, the most in the state, with about 7,000 in the highest-priority areas. Expect an onsite system in most rural areas.
- Kauai: The district health office (808-241-3321) gives rough groundwater guidance by town; for example, it lists Kekaha, Hanalei, Kilauea and Kapaa town as areas where cesspools discharge into groundwater. Have your TMK ready when you call.
- Maui: Follow the statewide DOH process above; we have not verified Maui County-specific grants.
Questions to ask before you sign
- Is sewer available to my lot, and if so, what would connecting cost compared with an IWS?
- Does my site need an ATU, or will a septic tank and leach field be approved?
- What is your contractor license class and number? (It must be A, C-9, C-37, C-37a or C-43.)
- Does the quote include engineering, permits, cesspool abandonment, restoration, and the final DOH paperwork?
- What will yearly maintenance or a service contract cost?
Need help getting started?
Call (808) 772-0705 or use the quote form, and tell us your island, town, whether you know the system type, and whether you are adding on or selling. We will work to route your request to an independent local company. For engineering and DOH approvals, you will also need a licensed civil engineer.
FAQ
When do I have to convert my cesspool in Hawaii?
State law (HRS 342D-72) requires every existing cesspool to be upgraded to an approved individual wastewater system or connected to a sewer before January 1, 2050, unless an exemption applies. A 2025 bill to move some deadlines to 2035 (SB 542) did not pass, according to the Department of Health.
Can I be required to convert before 2050?
Yes. The Department of Health lists triggers under HAR 11-62-06(m): a building modification that may change wastewater flow (such as adding a bedroom, bathroom or kitchen), a cesspool that has caused illness or nuisance conditions, one pumped more than twice in 12 months, one that has spilled more than once, or one that discharges directly into groundwater.
How much does a cesspool conversion cost in Hawaii?
Published figures vary by source and island. A 2021 state report put historical costs at about $9,000 to $60,000 or more. Wastewater Alternatives and Innovations estimated $25,000 to $50,000 in 2026. The Hawaii County task force reported a median of about $40,000 and an upper range near $70,000 on Hawaii Island. Get site-specific quotes.
Who do I hire to convert a cesspool?
Start with a Hawaii-licensed civil engineer, who designs the system and submits plans to the Department of Health. After approval, the work must be done by a contractor holding an A, C-9, C-37, C-37a or C-43 license. You may also need a licensed plumber or electrician.
How long does a cesspool conversion take?
The Department of Health says its plan reviews have averaged about 10 days, engineers have taken about 25 days on average to answer review comments, and construction of a new system has averaged about 200 days. Your project may be faster or slower.
Is there financial help for cesspool conversion?
A 2026 state law (HB 1618, Act 204) created a Cesspool Conversion Revolving Loan Fund run by the Hawaii Green Infrastructure Authority for low-interest or forgivable loans. As of October 20, 2026 the program was still under development with no application or terms posted. Kauai County has offered $20,000 reimbursement grants; its latest round closed October 6, 2026.
Do I have to convert my cesspool to sell my house?
The Kauai District Health Office says no, not at this time. The Department of Health warns that a buyer becomes responsible for bringing a non-compliant system into compliance, so expect the cesspool to come up in negotiations.
Sources
- Hawaii DOH Wastewater Branch: General info and FAQ (2050 deadline, early-upgrade triggers, fines, review and construction times; checked Oct 20, 2026)
- Hawaii DOH Wastewater Branch: Individual wastewater systems (step-by-step process, approved technologies, required contractor license classes, engineer list)
- Hawaii DOH: Financial support programs for cesspool conversion (statewide loan program, Kauai County grants, ended programs)
- Hawaii State Legislature: HB 1618 (2026) measure status (Cesspool Conversion Revolving Loan Fund; Act 204, July 8, 2026)
- Hawaii Public Radio: New loan program set to help homeowners finance cesspool conversions (June 25, 2026)
- Hawaii Green Infrastructure Authority: Cesspool conversion loan program (June 29, 2026)
- Hawaii DOH Kauai District Health Office: Wastewater FAQs ($100 plan review fee, Kauai groundwater guidance)
- Hawaii DOH: Cesspool Conversion Finance Research Report (2021, PDF)
- Hawaii DOH: Cesspool Conversion Working Group informational briefing (PDF) (low/average/high cost and monthly operating cost)
- Hawaii County Cesspool Conversion Task Force 2025 Report (PDF)
- Wastewater Alternatives and Innovations: Potty Portal technical assistance
- City and County of Honolulu ENV: Contact us (sewer connection permit and cesspool pumping numbers)
- Honolulu DPP Wastewater Branch: Sewer Capacity Analysis