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Tankless Water Heater Installation on the Big Island

Fast, reliable service – done right the first time.

Licensed and insured plumbers sizing and permitting tankless units correctly, from Kailua-Kona and the Kona coast through Waimea to Hilo and Puna. Upfront pricing.

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A tankless unit makes hot water on demand rather than storing it. This only works if the water reaching it has enough flow and pressure. On the Big Island, this is a real question because many homes run on catchment rather than county water. We size the unit to your house and water source, not just the box. Installation is only half the job. The other half is confirming your gas supply, venting, and water source can support it.

Our Tankless Water Heater Services on the Big Island

New Tankless Installation

A first tankless system in a home that has never had one. We size for peak simultaneous demand, confirm the gas line can handle the load, and plan the vent route before ordering anything.

Tank to Tankless Conversion

Swapping a failed storage tank for a tankless unit is not a like-for-like exchange. It usually requires a larger gas supply, new venting, and a different mounting position. We quote everything up front.

Propane and Gas Supply Sizing

Most Big Island homes run on propane rather than piped natural gas. We check the tank, regulator, and line size against the unit’s demands. An undersized supply is the most common reason a new tankless unit underperforms.

Venting and Combustion Air

A tankless unit vents differently from a tank. We install the manufacturer’s specified vent material and termination. We also confirm combustion air, which matters in the tight utility closets common in older homes.

Water Treatment and Scale Protection

Hard water and sediment shorten a heat exchanger’s life. We install sediment filtration and, where needed, a softener or scale inhibitor. We also fit isolation valves so you can flush the unit without cutting the pipe.

Catchment System Integration

In a catchment home, the pump and pressure tank determine if a tankless unit will fire reliably. We check pressure, flow rate, and filtration before recommending a model. We size the system around what your pump actually delivers.

Catchment Homes Change Which Tankless Unit You Can Install

This is the question almost nobody asks before buying. Tens of thousands of Hawaii residents draw household water from rainwater catchment rather than a county main. The University of Hawaii reports that most live on Hawaii Island, in the Puna, Kau, and Hamakua districts.

Catchment water does not arrive under municipal pressure. The CTAHR guidelines on rainwater catchment systems are direct about it. “To get water from the tank into your house, you need a pump system,” they say. The guidelines add that a pressurized system also needs “a pressure tank, check valves, and a pressure gauge” alongside it.

That matters for two reasons. A tankless heater needs a minimum flow rate to fire and steady pressure to hold a set temperature. A pump sized for a tank heater is not automatically sized for a tankless one. Get it wrong, and you get cold water sandwiches or a unit that cycles off mid-shower.

On a catchment home, we measure before recommending. We check delivered pressure and flow at the fixtures, the pump, pressure tank setting, and filtration. Then we pick a unit that suits it. If the pump needs upgrading, we say so in the quote, not after the heater is installed.

Our Tankless Installation Process

Every install follows the same sequence, whether a new build in Waikoloa or a tank swap in Hilo. We provide a written quote before ordering anything and handle the permit for you.

  1. Site visit and sizing. We measure peak demand, check the water source, and confirm gas supply and vent routing are workable.
  2. Written quote. Unit, scope, permit, and price in one document before we order anything.
  3. Permit application. We pull the work under our license with the County of Hawaii.
  4. Supply and venting work. We do gas line upsizing, vent installation, and combustion air before the unit goes up.
  5. Mount and connect. We set the unit, connect water and gas, and fit isolation valves for future flushing.
  6. Commission and test. We verify gas pressure, confirm the vent draws, set the output temperature, and run the fixtures.
  7. Inspection and handover. We meet the inspector, then show you the isolation valves, the filter, and the annual flush.

Nothing is signed off until the numbers are right at the fixture, not just at the unit. That is the difference between a heater that is installed and one that works.

Why Choose All Aloha Plumbing for Tankless Installation

We work across three Hawaiian islands, and the Big Island crew lives here. The person quoting your job already knows if your neighborhood uses county water or catchment.

  • Licensed CT-36812 and insured Hawaii plumbing contractor.
  • Big Island-based, with technicians on-island rather than flown in.
  • We pull permits under our license and meet the inspector.
  • Written pricing before anything is ordered.
  • We handle catchment and county water systems as routine.
  • Service agreements that keep your new unit performing.
  • We check propane supply sizing as part of every quote, not as an extra.
  • Financing available to spread a larger install over manageable payments.

Ask about current coupons and specials when you book, because they change and one offer applies per visit.

Ready for Endless Hot Water?

Tell us what you have now and where it is, and we can give you a straight answer on what a tankless unit would require. Book service or reach our Big Island team.

Want Consistent Hot Water?

Contact All Aloha Plumbing today and we will provide a clear upfront estimate.

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Tankless Water Heater Installation

Tankless Water Heater Installation FAQs

Will a tankless water heater work on a catchment system?

Usually yes, but it depends on your pump and pressure tank, not the heater. A tankless unit needs a minimum flow rate to fire and steady pressure to hold temperature. A pump sized for a storage tank is not automatically right for tankless. We measure delivered pressure and flow at the fixtures before recommending a model, and we note in the quote whether the pump needs work.

Do I need a permit to install a tankless water heater on the Big Island?

Yes. Hawaii County Code requires a permit to install, alter, replace, or convert water heating equipment and the piping serving it. The narrow exemptions cover clearing stoppages and like-for-like fixture swaps, not installing a water heater. We pull the permit under our license and meet the inspector, so the paperwork is ours.

Is propane a problem for a tankless unit?

Not at all, but the supply must be sized for it. Most Big Island homes run on propane rather than piped natural gas. A tankless heater draws far more gas at once than a storage tank. We check the tank, regulator, and line size against the unit’s demand. An undersized supply is the most common cause of a new tankless underperforming.

How long does a tankless installation take?

A straight replacement usually takes a single day when the gas supply and venting are adequate. A tank-to-tankless conversion normally takes longer because it often needs gas line upsizing and new venting. We provide the timeline in the quote, not on the day.

What maintenance does a tankless water heater need here?

An annual flush clears scale from the heat exchanger, and periodic filter changes keep it running smoothly. In catchment homes, sediment filtration matters more than with county water. We install isolation valves so you can flush the unit without cutting the pipe. Skipping the flush shortens a heat exchanger’s life.

Is a tankless water heater worth it on the Big Island?

It depends on how you use hot water. Tankless gives you endless hot water, reclaims the closet or wall space a tank occupies, and typically lasts longer than a storage tank. It costs more to install, especially for conversions that need gas and vent work. If your household runs several showers back to back, it earns its keep.

Real Customers • Real Stories

What Our Ohana Says

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“All Aloha came out super fast and fixed our leak the same day. Excellent service! These guys are real pros and treated my home with respect.”

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Hawaii Bottle Man

Kailua-Kona, Big Island

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“They replaced our water heater quickly and left everything spotless. The crew showed up exactly when they said they would. Couldn’t ask for better.”

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Ray Cabanting

Hilo, Big Island

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“Called at midnight with a burst pipe. They were here in 25 minutes and had it contained before the ceiling came down.”

TT

Thai Tran

Waimea, Big Island

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From the North Shore to Hilo, we’re proud to bring honest plumbing with aloha to homes across Hawaii.

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