Hawaii’s Cesspool Law: What Maui Buyers and Sellers Must Know

There are roughly 88,000 cesspools in Hawaii, and more than 12,000 of them are on Maui. Under state law, every single one has to go.

If you are buying or selling an Upcountry or rural Maui property, this is not a footnote. It is potentially a $20,000 to $50,000 line item, and it is one of the most common things I see buyers discover after they are already emotionally committed to a house.

What the law actually says

Act 125 requires all cesspools in Hawaii to be upgraded, converted, or closed by January 1, 2050. Not “encouraged.” Required. The replacement is an approved septic system or an advanced treatment or reuse system.

2050 sounds far away. It is not, in real estate terms. It is one ownership cycle. And the market does not wait for deadlines, it prices them in early. The closer we get, the more buyers will discount a cesspool property, and the more sellers will eat that discount at closing.

Why Hawaii is doing this

A cesspool is a hole. It puts untreated wastewater into the ground, and on an island that ground connects to the aquifer you drink from and the reef you swim on. The EPA has been on Hawaii about this for years, and the state finally set a hard date.

You do not have to love the law to have to comply with it.

What it costs

Real numbers: a septic system in Hawaii typically runs $20,000 to $50,000, and an enhanced or advanced system adds roughly $5,000 to $10,000 on top of that.

Cost varies with your lot. Slope, soil, access for equipment, distance to the house, and whether the system needs upgrading for a high-risk location all move the number. Upcountry lots with grade and limited access sit at the higher end.

The money most people do not know about

Two programs meaningfully soften this. A state tax credit of up to $10,000 per qualified cesspool. And a pilot grant program through the Department of Health offering up to $20,000 in reimbursement toward conversion or connection costs.

Stack those and a $35,000 conversion can land closer to $5,000 to $15,000 out of pocket. That is the difference between a dealbreaker and a negotiation. Almost nobody I talk to knows these exist.

If you are buying

Find out what the property has. Cesspool, septic, or county sewer. It should be in the seller’s disclosure, and if it is not, ask directly and in writing.

If it is a cesspool, get a real conversion quote during your inspection period, not a guess. Then use it. A documented $35,000 conversion cost is one of the most legitimate negotiation levers in a Maui transaction, and in a buyer’s market like mid-2026, sellers are listening.

If you are selling

You have a choice: convert before listing, or price it in and let the buyer do it.

Converting first removes an objection and widens your buyer pool. Not converting is fine too, as long as you are realistic. What does not work is hoping nobody asks. Every competent buyer’s agent asks, and finding it during inspection costs you more in renegotiation than disclosing it upfront ever would.

The Upcountry reality

Haiku, Makawao, Kula, and the rural stretches carry most of Maui’s cesspools, because that is where county sewer never reached. If you are shopping Upcountry, assume cesspool until proven otherwise, and budget accordingly.

Pair this with the water question and you have the two issues that define rural Maui buying. I wrote about the Upcountry water meter list separately.

The bottom line

This is not a reason to avoid Upcountry. It is a reason to go in with your eyes open and your calculator out. Every one of these costs is knowable before you write an offer. The people who get hurt are the ones who found out afterward.

Send me an address and I will tell you what the wastewater situation is and what conversion would realistically cost.

Mick St John, REALTOR with Compass in Haiku. (808) 281-9530 or mick@stjohnhawaii.com.

Figures from the Hawaii Department of Health and EPA, current as of 2026. Grant and tax credit programs have eligibility requirements and funding limits. Confirm current details with the Hawaii DOH and your CPA. General information, not legal or tax advice.