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A Guide to Home Wastewater Systems in Maui

Depending on where you live currently, you may not think much about where things go when you flush your toilet. If you are thinking of buying a home on Maui or a lot on Maui, you better know your s#%t or more specifically where it goes. This guide looks at the different types of wastewater systems used on Maui. For home buyers, this post identifies the various systems used on existing homes and potential due diligence items to consider during your purchase. If you want to build a new home, the post provides information about the costs and requirements for different types of systems.

Sewer System

There are large areas of the island that offer municipal sewer services. It is common but not exclusive in places like Kahului, Ka’anapali, Wailuku, Paia, Kihei, Wailea, Lahaina and more. With municipal systems, the discussion for buyers is pretty short. Maintenance and effort by the homeowner is limited. On occasion, older homes may need connections to the sewer system repaired or replaced. Similarly, owners may want to exercise caution planting trees with larger root systems proximate to the sewer system connections. Maui County sewer fees vary based on units on a property and whether the home uses public or private water.

There is one private sewer system that services a portion of Pukalani. Hawaii Water Service operates the system in Pukalani. They administer a number of private systems around the state.


Cesspools are the oldest type of individual wastewater system on island. They literally consist of a deep, covered, hole that collects waste. Sometimes the sides of cesspools consist of brick or concrete. Holes in the brick or concrete allow liquids to percolate out into the surrounding soils. The solids collect at the bottom of the cess pools with microbes breaking down the solid waste over time. A well functioning cesspool typically does not require pumping.

Cesspool Challenges

No pumping? Sounds great. What’s the catch? Well first and foremost, they tend to pollute the environment. Water from cesspools can introduce pathogens and excess nitrogen into the water table and the nearshore waters of the island. As a result, the state banned cesspools on new construction since 1992. Everything built after that needs to use a septic system. The EPA banned the use of any large capacity cesspool after 2005. The State of Hawaii passed legislation in 2017 requiring all remaining cesspools be converted to septic systems by 2050. Locations closer to the shoreline and streams are being prioritized for conversion as soon as possible.

While a well functioning cesspool doesn’t require pumping, some cesspools can and do fail over time. I can speak to that first hand. The cesspool failed at my home a couple of years ago when it stopped draining liquids. I caught it before it backed up into my house, but others are not so lucky.

Cesspool Due Diligence

If you are purchasing a home with a cesspool, appropriate due diligence is required. First and foremost, we recommend a cesspool inspection. This is not part of the standard home inspection. It would be a separate service with additional costs. Second, ask questions of the seller. Have they pumped their cesspool before? If so, when and how many times? Third, think about what upgrading to septic will entail. How easy will it be to convert to a septic system? Is it a big lot with plenty of space or is it a small lot with limited room for the equipment necessary to install a septic system or for the septic system itself?

Finally, it is important to budget for the cost of conversion. While it may still be quite a few years until 2050, demand will outstrip contractors as the deadline approaches. A scenario that requires earlier upgrades is also plausible. In addition to the aforementioned cesspool failures, the county can require earlier conversion if you plan to add additional bedrooms or bathrooms to your home.

Septic Systems

Homes built after 1992 without access to a sewer system use septic systems. A septic tank is an underground, watertight container. The tank is designed to hold the wastewater long enough for solids to settle to the bottom, and oils and grease to float to the top. Naturally occurring bacteria aid the separation process, break down the solids and reduce the volume of wastewater.

A concrete septic tank being installed on Maui
A Concrete septic tank being installed

The effluent, or partially treated wastewater, that remains in the septic tank after the separation process flows out of the tank through an outlet pipe and into the drainfield. The size of the septic tank and the drainfield depends on the number of bedrooms in a home. Regular maintenance and inspections of the septic tank are important to ensure that it is functioning properly and to avoid costly repairs.

The drainfield for a septic system during installation

They typically construct tanks out of concrete, fiberglass, or plastic. Most septic engineers recommend concrete where possible due to their superior durability. That said, with concrete tanks weighing 11,000 lbs, plastic may be the only option for some owners.

Aerobic Septic Tanks

An aerobic septic tank is a type of septic system that uses oxygen and aerobic bacteria to break down and treat wastewater. Unlike a traditional septic system, which relies on anaerobic bacteria to treat wastewater, an aerobic system uses an air pump or blower to inject air into the tank, creating an oxygen-rich environment that encourages the growth of aerobic bacteria.

The aerobic bacteria in the tank are more efficient at breaking down organic matter than anaerobic bacteria, which means that an aerobic septic tank can treat wastewater more quickly and effectively. This results in much cleaner effluent than that from a traditional septic system. The county requires these systems close to wells, streams and other potential water sources.

Septic Tank Maintenance

Septic tanks require periodic pumping as part of their ongoing maintenance. That helps remove sludge and solids at the bottom of the tank. Owners will need to expect to pump every 2-3 years.

Aerobic septic systems require more maintenance than traditional systems. The air pump and blower require regular inspection and maintenance to ensure continued Aerobic functionality. It is worth noting that users should be careful of their inputs into both Aerobic and Anaerobic septic systems. Too much cooking oil or grease can throw off the system. Bleach and other strong cleaning products may adversely impact the microbes that digest and separate wastes.

If you are buying a home with an existing septic system, inquiring about pumping history is the bare minimum required for septic due diligence. We recommend a septic inspection. Like a cesspool inspection, this would be an additional inspection above and beyond the home inspection.

Costs and Permitting Time Frames for Maui Septic Systems

It takes about four weeks to pull a permit for a new septic system. If you are located in a special management area, it will take longer. The cost for the permitting and engineering to design the system is about $4,000. Install typically run around $25,000. If you are installing an aerobic septic system near a well, you can expect permitting to take 4-6 months. Aerobic systems run from $30,000-$50,000 plus the ongoing maintenance costs.

Multiple Homes and Large Structures

Certain types of Maui county zoning can allow for multiple structures on a lot. You can have a maximum of two structures using one septic system. If there is a third residence on the property, you would need a second septic system.

Thinking of building a really big home? If you are wondering why you don’t see a lot of homes with six or more bedrooms in areas that don’t have sewer service, wastewater disposal is a big reason why. For homes with six or more bedrooms, the county requires a wastewater treatment plant. Those systems cost $50,000-$100,000 to install with a monthly cost of $1,800 to $2,500 a month. The monthly cost incurred covers monitoring, testing and maintenance.

Special Thanks to CDF Engineering

Thanks to Jake Freeman at CDF Engineering and Linda Taylor Engineering for providing most of the information in this post. Jake did the engineering of my cesspool to septic conversion. He is a great resource if you need assistance engineering and installing a septic system on Maui.

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