How to Check Your Cesspool Priority and TMK

By Hawaiʻi Cesspool Help · Published · 8 min read

Why Your Cesspool Priority Matters

Act 125 (2017) requires all approximately 88,000 cesspools in Hawaii to be replaced by 2050 — roughly 50,000 of them on the Big Island. The Hawaiʻi Department of Health assigned each property a priority level (Priority 1 through Priority 4) based on risk factors including proximity to drinking water wells, sensitive waters, and potential human health impacts.

Your priority level determines when you may need to act and can influence whether you qualify for state or county funding assistance. Understanding your priority is the first step in planning your cesspool conversion timeline. (S-1: DOH Cesspools page; S-5: Act 125 legislative report)

Important: County-level enforcement timelines for each priority category are still being developed. While the prioritization framework is established, specific deadlines by priority level have not been finalized at the county level. (Caveat C-4: statewide categories; Big Island-specific enforcement timeline not yet published)

Understanding the Four Priority Categories

The Hawaiʻi Department of Health defines four cesspool priority categories:

Priority 1 (Significant Risk)

Cesspools that present a significant risk of human impacts, drinking water impacts, or are draining to sensitive waters. These represent the most urgent replacements in the prioritization framework. (S-1: DOH Cesspools page — P1 definition confirmed live)

Priority 2 (Drinking Water Potential)

Cesspools with potential to impact drinking water sources. While not classified as significant risk, these properties still require attention under the statewide replacement timeline. (S-1: DOH Cesspools page — P2 definition confirmed live)

Priority 3 (Sensitive Waters Potential)

Cesspools with potential to impact streams, nearshore waters, or other sensitive environments. Environmental risk is the primary factor for this category. (S-1: DOH Cesspools page — P3 definition confirmed live)

Priority 4 (Pending Analysis)

Properties where the Department of Health has not yet completed the full risk assessment. Priority 4 does not mean "no risk" — it means the analysis is still in progress. (S-1: DOH Cesspools page — P4 definition confirmed live)

Note: These priority categories are statewide (all Hawaiian islands). Big Island properties follow the same framework, but the number and distribution of priorities differs by island. (Caveat C-4: statewide vs. county-specific distinction)

After you find your result, read what a cesspool priority rating means for a plain-language explanation of the current red, orange, and yellow map levels and the limits of what a rating can establish about one property.

How to Check Your Property's Cesspool Priority

There are two main ways to determine your property's cesspool priority level:

Step A — Use the Interactive Prioritization Tool

The University of Hawaiʻi Sea Grant Program developed an interactive map tool in collaboration with the Department of Health that ranks cesspools by risk to groundwater, drinking water wells, streams, and nearshore waters. You can enter your address or navigate to your property on the map to see its priority classification.

Caveat: The exact web address for this tool should be confirmed by visiting the Hawaiʻi DOH Wastewater Branch page for the current link, as Sea Grant URLs may change. The tool visualizes priority categories assigned by DOH — it is a lookup and visualization resource, while DOH remains the authoritative source for priority assignments. (S-3: UH Sea Grant map tool; Caveat C-1: URL unverified during research)

Step B — Contact the Department of Health Directly

If the interactive tool is unavailable or you prefer direct confirmation, contact the Hawaiʻi County Department of Health Wastewater Branch at (808) 961-8252 with your TMK number. They can provide information about your property's priority classification. (S-1: DOH contact reference)

What Is a TMK and Why You Need It

Tax Map Key (TMK) is Hawaii's equivalent of a parcel or APN number used in other states. It uniquely identifies every piece of land on the Big Island. All government agencies — including DOH, the Board of Land and Taxation (BOLT), and planning departments — use your TMK to reference your property.

You will need your TMK for:

TMK format on the Big Island: Typically appears as X-Y-TZ (e.g., 3-2-015:001) where X = district, Y = zone, TZ = tax zone. (S-4: BOLT property search — TMK as Hawaii's parcel identifier)

Where to Find Your TMK Number

You can locate your TMK without visiting the county through four methods:

  1. Property tax bill — Look for "Tax Map Key" or "TMK" on your annual Hawaii County property tax statement.
  2. Your deed — The TMK is listed in the legal description of your property title.
  3. Hawaii County BOLT online search — Visit hawaiicounty.gov and search the Board of Land and Taxation property database by address or owner name. (Caveat C-2: county website works through normal browsers)
  4. Call BOLT directly — Hawaii County Board of Land and Taxation at (808) 961-8273.

If the online portal is down or difficult to navigate, phone contact with BOLT is the most reliable fallback. (S-4: BOLT property search; secondary methods from general knowledge of Hawaii property systems)

Putting It Together — From TMK to Priority Check

Here is a concrete workflow that combines both lookups:

  1. Find your TMK using one of the methods in Section 5 above.
  2. Open the Sea Grant cesspool prioritization tool or call DOH with your TMK number to check your priority level.
  3. Identify your priority category (P1–P4) and understand what it means using the definitions in Section 2 above.
  4. If you have a cesspool, determine whether replacement is required for your property and explore funding options through the resources below.

This workflow synthesizes information from separate government sources — no single agency provides both priority lookup and TMK identification in one place. The value of this guide is combining these two processes into a single homeowner-friendly path. (Caveat C-3: synthesis of two separate agency workflows)

Get a Personalized Timeline for Your Property

Important Disclaimers

The DOH is the authoritative source for priority assignments. The Sea Grant tool visualizes this data but does not replace official DOH determinations. (Caveat C-5: do not promise specific replacement deadlines per priority level)

This article is for informational purposes only and does not constitute legal or engineering advice. Priority assignments may be updated by the Department of Health as new data becomes available. Hawaiʻi Cesspool Help coordinates between homeowners and licensed professionals. It does not provide engineering services directly.