Septic Installation & Cesspool Conversion in Waiakea and Waiakea Uka

We install septic systems and convert cesspools across Waiakea, from the town streets near Hilo Bay up to the larger mauka lots of Waiakea Uka, about 15 to 25 minutes from our Keaau yard depending on how far up the hill you live. Waiakea is less a single neighborhood than a long strip of land. It runs from Hilo Bay up the slope of Mauna Loa, and the wastewater picture changes as you climb.

Waiakea at a glance

  • An old land division. Waiakea is a traditional ahupuaa that stretches for miles from Hilo Bay to Waiakea Uka on the lower flanks of Mauna Loa.
  • Not its own Census place. The 2020 Census lists no Waiakea or Waiakea Uka place in Hawaii County. The town side falls within the Hilo CDP (44,186 people in 2020), so we use census tracts below.
  • Density drops as you climb. Census tracts don’t follow neighborhood lines, but they show the pattern. The Hilo tract named “University-Houselots” holds about 2,600 housing units on 2.4 square miles. The mauka tract named “Upper Waiakea Forest Reserve” holds about 730 units spread over 245 square miles, most of it forest (ACS 2020 to 2024 estimates).
  • Two more Hilo tracts, named Puainako and Kawailani, hold about 2,180 and 1,900 housing units on 1.8 and 1.2 square miles.
  • Rain: Hilo Airport’s 30-year normal is about 130 inches a year. A Waiakea Uka rain gauge logged roughly 26 inches more than the airport in August 2013 alone.
  • Water flows to the bay. Waiakea Stream runs off Mauna Loa and empties into Waiakea Pond near sea level.
  • Hilo Bay priority area. DOH’s 2017 report named Hilo Bay one of five Hawaii Island cesspool priority areas, with about 8,700 cesspools.

How growth moved mauka

Lower Waiakea is close-set town housing on small lots. Go far enough up the hill and the lots get bigger and the houses farther apart, and in Waiakea Uka you start to see cattle land and a state forest reserve. Some of Hilo’s more expensive homes are up there too.

That spread matters for septic work. On the smaller in-town lots, the question is usually whether a tank and leach field fit at all once you account for the house, driveway and setbacks. State rules set aside 10,000 square feet per system, though lots recorded before August 30, 1991 are exempt. On the bigger mauka lots, room is rarely the issue. Rock, rain and slope are.

Building or converting in Waiakea Uka

Mauka Waiakea sits on Mauna Loa lava. During the 1880 to 1881 eruption, observers reported Waiakea Uka forests burning as the flow moved toward Hilo. Its southern lobe crossed what is now Komohana Street and stalled near Mohouli and Popolo streets. In 1984, many people thought the flow coming off Mauna Loa was headed for Waiakea Uka. It ended up aimed at upper Kaumana instead and stopped well short of town.

What that leaves underfoot varies from lot to lot. Some properties have a decent layer of soil, and others are close to bare rock. The engineer’s percolation test and 5-foot soil profile decide which. Where the profile hits fractured lava, HAR 11-62 calls for a soil replacement system with at least 3 feet of separation to groundwater. That means excavating the rock and bringing in suitable fill, which is where much of the extra cost on a mauka job comes from.

Rain is the other design driver. With well over 100 inches a year, the ground stays wet and stormwater runs across lots on its way downhill. We want the leach field placed where surface water won’t sit on it, and we plan excavations around the weather.

Typical projects across Waiakea

  • Cesspool conversions on older in-town homes, usually on tight lots where the layout takes some care.
  • New homes on larger mauka parcels, where the system is part of the building permit. DOH reviews the wastewater plan before the county building permit is signed off. See septic requirements for a new home.
  • Ohana units and additions, which often push a home over a design limit. One system serves at most five bedrooms and 1,000 gallons a day, and any room of 70 square feet or more counts as a bedroom.
  • Pre-sale planning. A sale doesn’t force a conversion in Hawaii, but buyers ask. Our guide on buying or selling a home with a cesspool covers what to expect.

Sewer: check before you design

Parts of Hilo are on county sewer and parts are not, and we won’t guess which streets are which. Before paying for a septic design, call the County of Hawaii Department of Environmental Management and ask whether sewer is available at your address. Where it is, county code generally expects you to connect.

Sewer service is also being reviewed. Under a 2024 agreement with the EPA, the county has to develop a sewer service expansion program by the end of 2026 and an integrated wastewater master plan by early 2027. The county has also said it is using a 2025 UH Hilo study of sewage reaching Hilo’s coastal waters to help prioritize sewer line expansion in Hilo. None of that tells you what will happen on your street, so ask DEM directly.

Deadlines and financing

Every cesspool has to be upgraded, converted or connected to sewer by January 1, 2050. Being in the Hilo Bay priority area doesn’t create an earlier deadline, though DOH can require an earlier upgrade in some cases, such as when a permit adds bedrooms. You can look up your parcel’s rating on the UH Hawaii Cesspool Prioritization Tool. Our priority map guide explains the colors.

On money: the Act 204 state loan fund is expected to open in late 2026. USDA Section 504 loans and grants for lower-income owners are handled from the Hilo office. The program has rural-area rules, so check eligibility for your address.

Close to Waiakea

Planning a project in Waiakea?

Tell us where in Waiakea you are and what you have in mind: a conversion, a new home or an addition. We’ll walk the property and explain what the ground and the rules will likely require. Request a free estimate

Frequently Asked Questions

Is Waiakea Uka on county sewer?

We can’t answer that street by street, and you shouldn’t rely on a guess. Ask the County Department of Environmental Management about your address before you pay for a septic design.

Why does a mauka Waiakea system often cost more than one in town?

It usually comes down to rock. Many mauka lots sit on Mauna Loa lava with little soil, and fractured lava calls for a soil replacement system, which means more digging and imported fill.

Does the heavy rain up here affect the design?

Yes. Waiakea Uka can get noticeably more rain than the airport. The leach field needs to sit away from where runoff collects, and wet ground can slow the installation.

My in-town lot is small. Can I still convert?

Often, yes. Lots recorded before August 30, 1991 are exempt from the 10,000 square foot rule, but the 5-foot setbacks still apply. The engineer will check whether a tank and field fit.

Does being in the Hilo Bay priority area mean I have to convert sooner?

Not by itself. The statewide deadline is January 1, 2050 for every cesspool. DOH can require an earlier upgrade in specific cases, like adding bedrooms under a building permit.

Does Mauna Loa’s lava history affect my permit?

It mainly affects the ground. Younger flows tend to have less soil, which changes the system type. Ask the county about lava hazard designations for your parcel when you plan a new home.