What is an aerobic treatment unit?

An ATU is an on-site wastewater system that treats sewage with oxygen. A blower pumps air into the treatment chamber, aerobic bacteria break the waste down far more completely than the anaerobic process in a septic tank, and the treated water leaves clean enough to be dispersed in a much smaller area. It is one of the three cesspool conversion paths, alongside a conventional septic system and a sewer connection.

Do I need an ATU or a regular septic system?

The site assessment decides. A conventional septic system needs room for a drain field and soil that percolates; where the lot is under the Department of Health’s 10,000-square-foot rule, the soil is clay or rock, or the water table is high, the design moves to an ATU. If a standard system will work on your lot we will tell you — it is usually the simpler and cheaper option.

Does an ATU need electricity and maintenance?

Yes to both. The blower runs on household power, the control panel carries an alarm, and the unit has to be inspected and pumped on a schedule. It is more to look after than a septic tank, and that is the trade for a system that works where a tank and drain field cannot.

Does an ATU need a Department of Health permit?

Yes. Like any new or replacement individual wastewater system in Hawaiʻi, the design is engineered and approved by the Department of Health before any digging starts, and inspected once it is in. We file and track the permit as part of the job.

Do you service aerobic treatment units?

Yes. We pump and service ATUs across Oʻahu. If the alarm is on, the unit smells, or it has simply not been looked at in a while, call (808) 630-9966.

How much does an aerobic treatment unit cost on Oʻahu?

It depends on the unit, the design and the ground it goes into. We quote after the free assessment, not over the phone, and the estimate is in writing before anything begins. Our Hawaiʻi cesspool conversion guide breaks down what a full conversion costs stage by stage.

Aerobic Treatment Units (ATU) in Honolulu & Oʻahu

new on-site wastewater system being installed on Oʻahu

Aerobic treatment units on Oʻahu

An aerobic treatment unit does in the tank what a septic system leaves to the ground. A blower pumps air into the treatment chamber, aerobic bacteria break the waste down far more completely than the anaerobic process in a conventional tank, and the water that leaves is clean enough to be dispersed in far less area — which is why it is the answer on lots where a standard drain field will not fit or the soil will not take one. Golden Penny Sanitation Inc. installs and services ATUs across Oʻahu. We are a licensed and insured Hawaiʻi sanitation contractor — Hawaiʻi License CT-39138 — and the unit goes in on an engineer’s design with the Department of Health permit in hand.

The assessment that decides whether you need one is free. Call (808) 630-9966.

ATU installation as a cesspool conversion — the third of the three conversion paths
ATU as a replacement where a conventional drain field has failed and cannot be rebuilt
System design by a licensed engineer and Department of Health permitting, handled as one job
Tank, blower, control panel and dispersal installed and started up by one crew
Routine ATU pumping and service after the install
Free, no-obligation inspection and estimate

When an ATU is the right answer

An ATU is not the default, and nobody should sell you one from the curb. It is what the site assessment points to when a conventional septic system cannot legally or physically go in:

Small lots — the Department of Health requires 10,000 square feet of land per system, and many older Oʻahu lots fall short
Soil that will not percolate — clay and rock that fail the percolation test
A high water table, where trenches cannot keep the three feet of separation from groundwater the rules require
Shoreline, stream-side and well-adjacent properties — the same factors that put a cesspool in a high priority level
A failed drain field on a lot with no fresh ground left to rebuild it in

Where the ground and the lot will take a standard drain field, that is usually the simpler and cheaper system, and we will say so. The rules that decide it are set out in our conversion guide, and the drain field page covers the conventional side.

What installing an ATU involves

An ATU is a permitted individual wastewater system, so the sequence is the same as any conversion: assess, design, permit, build, inspect. The difference is what goes in the ground and what it needs afterward.

Site and soil assessment — the existing system is pumped and opened, the lot and soil evaluated
Engineered design of the unit and its dispersal, sized to the bedroom count
Department of Health permit approved before any ground is broken
Installation — the treatment tank, the blower and control panel, the electrical connection, the dispersal
Start-up and inspection, and the old cesspool pumped and closed if this is a conversion
Routine service afterward — an ATU has a pump and a blower, and it needs to be looked at

One honest difference from a septic tank: an ATU needs electricity and attention. The blower runs, the control panel has an alarm, and the unit has to be inspected and pumped on a schedule. That is the trade for a system that works on ground where nothing else will.

What an aerobic treatment unit costs

The unit, the design and the ground it goes into all move the number, so we quote after the assessment, not before. Estimates are free and in writing. Our Hawaiʻi cesspool conversion guide breaks down what a full cesspool conversion costs stage by stage.

ATUs and cesspool conversion

Hawaiʻi law requires every cesspool to be upgraded, converted to septic, or connected to a sewer by January 1, 2050, and for a share of Oʻahu’s cesspool lots — small, close to the water, on poor soil — the septic path means an aerobic treatment unit rather than a tank and drain field. Our Hawaiʻi cesspool conversion guide covers the law, the three options and the costs; cesspool conversion is the job itself, and this is the system it ends in when the ground says so.

sanitation crew servicing a system on Oʻahu

Meets the 2050 requirement on lots a conventional system cannot
Engineered design and Department of Health permit handled for you
Treatment in the tank, so far less ground is needed for dispersal
One licensed crew from assessment to start-up
Ongoing pumping and service from the people who installed it

Frequently Asked Questions

What is an aerobic treatment unit?
An ATU is an on-site wastewater system that treats sewage with oxygen. A blower pumps air into the treatment chamber, aerobic bacteria break the waste down far more completely than the anaerobic process in a septic tank, and the treated water leaves clean enough to be dispersed in a much smaller area. It is one of the three cesspool conversion paths, alongside a conventional septic system and a sewer connection.
Do I need an ATU or a regular septic system?
The site assessment decides. A conventional septic system needs room for a drain field and soil that percolates; where the lot is under the Department of Health’s 10,000-square-foot rule, the soil is clay or rock, or the water table is high, the design moves to an ATU. If a standard system will work on your lot we will tell you — it is usually the simpler and cheaper option.
Does an ATU need electricity and maintenance?
Yes to both. The blower runs on household power, the control panel carries an alarm, and the unit has to be inspected and pumped on a schedule. It is more to look after than a septic tank, and that is the trade for a system that works where a tank and drain field cannot.
Does an ATU need a Department of Health permit?
Yes. Like any new or replacement individual wastewater system in Hawaiʻi, the design is engineered and approved by the Department of Health before any digging starts, and inspected once it is in. We file and track the permit as part of the job.
Do you service aerobic treatment units?
Yes. We pump and service ATUs across Oʻahu. If the alarm is on, the unit smells, or it has simply not been looked at in a while, call (808) 630-9966.
How much does an aerobic treatment unit cost on Oʻahu?
It depends on the unit, the design and the ground it goes into. We quote after the free assessment, not over the phone, and the estimate is in writing before anything begins. Our Hawaiʻi cesspool conversion guide breaks down what a full conversion costs stage by stage.