If you’re buying a home in Hawaii, or already own one, the topic of cesspools is going to come up sooner or later. Hawaii is the only state that still allows large numbers of cesspools, and while they’ve been the go-to wastewater system in rural areas for decades, their days are numbered. A 2017 state law set a mandatory deadline of 2050 for all cesspools to be converted to approved systems like septic or sewer. That means buyers, sellers, and homeowners need to understand not just what cesspools are, but what the conversion process involves.

Here’s a straightforward guide to the difference between cesspools and septic, why Hawaii is phasing cesspools out, and what you should plan for if you’re thinking about buying property here.

What’s the Difference Between a Cesspool and Septic System?

Cesspools are simple pits in the ground lined with concrete or stone that collect household wastewater. There’s no treatment — liquid seeps into the soil, and solids accumulate at the bottom. They’re cheap and easy to build, which is why they became so common across Hawaii in the 20th century.

The problem? Cesspools release raw sewage into the ground, and that can contaminate groundwater, streams, and nearshore waters. This is a serious issue in Hawaii, where clean water and coral reef health are critical to the environment and economy.

Septic systems, on the other hand, include a tank that separates solids from liquids and allows bacteria to break down waste before effluent is discharged into a leach field. It’s not perfect, but it dramatically reduces pollution risks compared to cesspools.

For buyers, the difference is huge: a property with a septic system is typically more compliant with future regulations and less likely to face expensive near-term upgrades.

Why Hawaii Is Requiring Cesspool Conversions by 2050

In 2017, lawmakers passed Act 125, which requires the conversion of all cesspools in Hawaii by the year 2050. The law was driven by environmental concerns: roughly 88,000 active cesspools statewide discharge more than 50 million gallons of untreated wastewater into the ground every single day.

The Department of Health (DOH) has identified cesspools as a major threat to drinking water supplies, recreational waters, and coral reefs. In fact, many cesspools are located close to coastal areas, streams, or aquifers — meaning the wastewater doesn’t just stay in the backyard, it eventually makes its way into the water table and the ocean.

The 2050 deadline may sound far off, but the conversion effort is massive. Spreading it over decades is meant to give homeowners and counties time to upgrade without overwhelming contractors or creating financial crises. Still, buyers should understand that the requirement is real and will eventually apply to every cesspool property in Hawaii.

 

Where Are Cesspools Most Common in Hawaii?

Cesspools are scattered across every island, but they are most common in older and more rural communities. According to the Hawaii Department of Health, there are still more than 88,000 active cesspools statewide, with the highest concentration on the Big Island.

  • Big Island: Roughly half of all cesspools in Hawaii are here. Many rural subdivisions and older neighborhoods still rely on them.
  • Maui: Thousands remain, especially in Upcountry and Hana areas where sewer lines are limited.
  • Kauai: Rural towns and coastal areas still have cesspools that sit close to streams and groundwater.
  • Oahu: Fewer compared to neighbor islands, but still present in pockets of older communities not connected to city sewer.

The Department of Health has an interactive cesspool map that shows where systems are located and which ones fall into priority zones. These maps are valuable for buyers who want to know if a property is likely to need conversion sooner rather than later. See the DOH cesspool map

What Triggers a Mandatory Cesspool Conversion?

Even though the statewide deadline is set for 2050, there are situations where you may be required to convert much sooner. Common triggers include:

  • Property sale: Some cesspools located in priority areas must be upgraded during or before transfer of ownership.
  • Major renovations: Applying for large building permits can trigger a requirement to upgrade the wastewater system.
  • Environmental risk zones: Properties near streams, wells, or shorelines may fall into Tier 1 priority zones where early conversion is required.
  • County ordinances: Some counties are considering additional rules that could shorten the timeline for high risk areas.

For buyers, this means it is critical to check the cesspool status of a property before closing. A home inspection alone may not cover wastewater systems in detail, so requesting records from the seller or county can save major surprises later.

How Much Does It Cost to Convert a Cesspool to Septic?

Costs vary widely by island, lot size, soil, slope, access for equipment, and whether you can connect to sewer instead of installing a new onsite system. A realistic planning range for a standard single family home is often $20,000 to $40,000, and complex sites can run higher. That total typically includes design by a licensed engineer, permits, excavation, the tank and leach field or an advanced treatment unit, and inspection fees.

Three cost drivers to watch:

  • Soil and groundwater: Shallow groundwater, lava rock, or heavy clay soils can require engineered solutions or aerobic treatment units.
  • Distance and access: Long pipe runs, retaining walls, or tight sites raise excavation and labor costs.
  • System type: Conventional septic is usually less expensive than an advanced treatment unit, but site conditions may require advanced treatment to protect groundwater.

For background on prioritization and why some properties need higher spec systems, review the Hawaii DOH and Sea Grant resources. These explain how priority areas were identified and why certain sites carry higher contamination risk.
DOH Prioritization Report
and
Hawai‘i Cesspool Prioritization Tool.

State and Federal Programs That Help With Costs

Funding has come in waves. Some programs are periodic or county specific, so it is smart to check current availability before you budget.

  • State DOH pilot grants: The Department of Health launched a pilot program offering up to $20,000 in reimbursements for conversions or sewer connections, targeted to low and moderate income households. Program windows have opened and closed, so check the DOH newsroom and funding page for current status.
    DOH pilot grant announcement and
    DOH funding status.
  • Hawaii income tax credit: Lawmakers created a cesspool upgrade, conversion, or connection income tax credit, historically up to $10,000 per qualified cesspool, certified by DOH. Availability and details have changed over time, so confirm the most recent session language and whether credits are currently active.
    HB 440 (2023 session) and
    HB 1396 text.
  • County programs: Counties may offer their own grants. For example, Kaua‘i announced grants of $20,000 each for eligible homeowners, with limited slots and waitlists.
    Kaua‘i Residential Cesspool Conversion Grant.
  • USDA Rural Development: Several USDA programs can support wastewater improvements through loans or grants administered by nonprofits or local governments. Ask lenders and county housing agencies which USDA options are currently active on your island.
    USDA Rural Decentralized Water Systems and
    USDA Water and Waste Disposal.

Tip for buyers and sellers: confirm the property’s location in the state priority map and ask your contractor if that status affects eligibility for grants or the required system type.
DOH cesspool overview.

What Buyers and Sellers Should Watch Out For

If you are buying or selling a home in Hawaii, wastewater systems need to be part of your due diligence. Cesspools can affect financing, insurance, and long term costs.

  • Disclosure obligations: Sellers must disclose whether a property uses a cesspool. Buyers should review this carefully and confirm with county records.
  • Inspection limitations: Many home inspections do not include in depth wastewater evaluations. Hire a specialist or request documentation from the seller.
  • Lender requirements: Some lenders may require proof of septic or sewer compliance before approving financing. Rural areas are especially sensitive.
  • Title and escrow: Ask your escrow officer to flag wastewater system issues early. This avoids surprises right before closing.

Including cesspool status in your purchase checklist is as important as checking roof age or flood zone status. It can make or break the financial picture of a property.

What Happens If You Do Not Convert by 2050?

The 2050 deadline is written into state law. While enforcement mechanisms are still being developed, several likely outcomes are on the horizon:

  • Fines and penalties: Owners who fail to convert could face escalating fines as the deadline approaches.
  • Permit restrictions: Counties may block new building permits for properties that are not compliant.
  • Transfer complications: Future property sales may be delayed or canceled if a cesspool has not been converted.
  • Environmental enforcement: High risk cesspools, especially near coastlines and wells, could be targeted for earlier enforcement actions.

The message is clear: conversion is not optional. The sooner homeowners plan and budget, the smoother the transition will be.

Frequently Asked Questions

Q: Can tourists or short term renters be affected by cesspool laws?
Indirectly yes. Rental property owners must comply with cesspool conversion rules, which can affect availability and costs for vacation rentals.

Q: Is connecting to a sewer system cheaper than building a septic?
If your property is near an existing sewer line, connection is usually the most cost effective solution. However, distance and permitting can raise costs.

Q: Do cesspools affect property value?
Yes. Properties with cesspools may sell for less, especially if they are in priority areas where conversion will be required soon.

Q: How do I check if a property is in a priority zone?
Use the Department of Health cesspool maps, which identify high risk areas and conversion timelines.

Final Thoughts

Cesspools are still common across Hawaii, but they are on their way out. Every homeowner will eventually need to address conversion, and buyers should factor this into their decision making process today. Waiting until 2049 will only increase costs and stress. Planning ahead, researching grants, and talking to contractors now can save thousands later.

For the latest updates, check with the Hawaii Department of Health, your county permitting office, and local news on cesspool conversion programs. Staying proactive will keep you compliant and protect Hawaii’s water resources for future generations.

 

 

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