How Rinnai Tankless Water Heaters Work
Learn how Rinnai tankless systems deliver efficient, on-demand hot water and why they’re a reliable choice for Atlanta homeowners.
What Is a Rinnai Tankless Water Heater?
A Rinnai tankless water heater is a gas-powered, wall-mounted unit that produces hot water on demand. It stores no water, so there is no tank to keep warm between uses and no supply limit to run out of.
Rinnai is a Japanese manufacturer with over a century of production experience. Their residential tankless units carry Energy Star certification and deliver flow rates from 4 to 11 gallons per minute, depending on the model. That range covers a single bathroom up to a large home running multiple fixtures at the same time.
A properly maintained Rinnai unit routinely reaches 20 or more years of service life, well above the 8 to 12 years typical for standard tank water heaters.
How Does a Rinnai Tankless Water Heater Work?
Every hot water call runs through the same sequence. Here is each step in order.
You open a hot water tap
Cold water enters the unit through the cold water inlet pipe.
The flow sensor activates
The sensor detects water movement and sends a signal to the control board to begin the heating cycle.
The gas burner ignites
The control board opens the gas valve and fires the burner through direct ignition. No standing pilot light burns gas between uses.
Water moves through the heat exchanger
Cold water travels through a coiled tube positioned directly above the burner. The tube absorbs heat from the flame and transfers it to the water passing through.
The unit modulates output
A modulating gas valve adjusts burner intensity in real time based on incoming water temperature and your target output setting. This keeps the water at a consistent temperature even as flow changes or multiple fixtures open at once.
Hot water reaches your tap
Heated water travels from the heat exchanger through your home’s supply lines to the open fixture.
The burner shuts off
When you close the tap, the flow sensor detects zero movement and the burner stops immediately. The unit draws no gas until the next hot water call.
The time from activation to hot water at the unit is roughly two to three seconds. How long it takes to reach your tap depends on the distance between the unit and the fixture.
Key Components Inside a Rinnai Tankless Unit
Knowing what each part does helps you follow a technician’s explanation during a service call and catch early warning signs between visits.
Flow Sensor
The flow sensor sits at the cold water inlet. It reads water movement and triggers the heating cycle. Most Rinnai residential models require a minimum flow rate of 0.4 to 0.5 gallons per minute to activate. Flow below that threshold keeps the burner off, protecting the heat exchanger from running dry.
Heat Exchanger
The heat exchanger is the core of the unit. It transfers thermal energy from the burner flame to the water flowing through the coiled tube inside it. Rinnai uses stainless steel or copper heat exchangers depending on the model series. Scale from mineral deposits builds up on the inner walls of the tube over time, reducing heat transfer. Annual descaling keeps this part at rated performance and extends the unit’s service life.
Modulating Gas Burner
The burner generates heat. The modulating gas valve adjusts fuel delivery from moment to moment. This modulation keeps output temperature steady when hot water demand spikes or when Atlanta winter temperatures drop the incoming cold water temperature below its summer baseline.
Venting System
Rinnai residential units use a two-pipe direct vent setup. One pipe draws fresh combustion air in from outside the home. A second pipe exhausts combustion gases back outside. Proper venting is required by Georgia building code and prevents combustion byproducts from entering living spaces. All installations across Fulton, Gwinnett, Cobb, and DeKalb counties must meet this standard.
Digital Control Board
The control board manages every unit function. It reads sensor data, governs the gas valve, tracks fault codes, and displays the output temperature setting. Rinnai’s optional Wi-Fi module connects to this board and lets you adjust the set temperature from a smartphone without going to the unit.
Rinnai Tankless vs. Tank Water Heaters
Standard tank water heaters store 30 to 80 gallons and maintain that temperature around the clock. Keeping stored water hot when nobody is using it is called standby heat loss. The U.S. Department of Energy estimates standby loss accounts for 10 to 15 percent of a home’s water heating costs.
Rinnai tankless units produce no standby heat loss. The burner runs only when hot water is actively flowing. For households using 41 gallons or less of hot water per day, the DOE reports that tankless heaters can be 24 to 34 percent more energy efficient than storage tank models.
The trade-off is a higher purchase price and a more involved installation. A tankless unit costs more upfront than a standard storage tank. The payback comes through lower monthly utility costs and a longer service life. Rinnai backs each unit with a 12-year heat exchanger warranty and a 5-year parts warranty.
Is a Rinnai Tankless Water Heater Right for Your Atlanta Home?
A Rinnai tankless unit fits homes that:
One Atlanta-specific factor to plan for is water hardness. Atlanta’s water supply comes from Lake Lanier and the Chattahoochee River. Most Metro Atlanta ZIP codes have moderate mineral content that deposits scale inside the heat exchanger over time. Scheduling annual descaling, or pairing the unit with a whole-home water softener, protects the heat exchanger and keeps efficiency at the rated level year after year.
Rinnai Tankless Water Heater Installation in Atlanta, GA
Installing a Rinnai unit properly requires gas line sizing, two-pipe vent fabrication, and sometimes a dedicated electrical circuit for the control system. Each of these steps requires a licensed plumber. Most Atlanta-area jurisdictions also require a permit before work begins.
Plumbing Express installs Rinnai tankless water heaters throughout Metro Atlanta. We serve ZIP codes 30301, 30305, 30309, 30319, 30326, 30327, 30338, 30339, 30340, 30342, and 30350, along with surrounding communities across Fulton, Gwinnett, Cobb, and DeKalb counties.
Our process on installation day: we size the unit to your home’s peak demand, run and seal the vent pipes, verify gas supply pressure, test combustion output, set your preferred temperature, and walk you through the control panel before we leave. For accurate pricing on your job, contact our team for an exact quote. Final cost depends on the Rinnai model selected, your current gas line configuration, and the vent run distance to an exterior wall.
Related Services From Plumbing Express
Reviewing your home’s plumbing system at the same time as your water heater upgrade saves you a second service call. Our team handles these services across Metro Atlanta:
What Atlanta Homeowners Say About Plumbing Express
Our 4.9-star rating comes from 2,000+ Google reviews written by real homeowners across Metro Atlanta. Here is what a few of them had to say.
Read more reviews on Google or visit our customer reviews page to see why Atlanta homeowners choose Plumbing Express.
Service couldn’t be completed due to needing a new system. We appreciate the very informative visit as well as insight that could help after a new unit install.
Plumbing Express was great. I had a failed sump pump that had partially overflowed into the basement. Nasty. Josh was the tech that did the work. He was efficient, neat and courteous. I will use Plumbing Express if I have any other plumbing needs and I will recommend them to my family and friends.
The technician was very knowledgeable and professional. I believe they did a very good job.
Ron was our second plumber from this company. The first plumber came, examined pipes and said he found no leak, even though we had experiences a large amount of water leaking from the ceiling in the finished basement. Several days later we had another leak-same area but less water the second time. Ron came in, listened to our frustration and did a more thorough inspection of the pipes and identified the problem. He was very personable and professional. On his third visit, we had several replacement pipes installed and are without leaks again. Our frustration, with the situation, was my son had used your company to replace pipes when he purchased the home and founding out not all the pipes were included with that process.
Tim arrived on time and was very professional. He took his time to explain the problem and the process it would take fix the water line.
Called Plumbing Express as tankless hot water not operating. Their website states "Get Free Plumbing Quote ". When service man showed up an looked at unit he said there would be a $207 charge to look into unit in order to give me a quote to fix unit. Due to not having hot water and time required to get another company to address the problem I agreed to pay $207 for quote. After looking in unit I was told he would not be able to fix due to age of unit and parts not available. I think he should have said parts not available when seeing model number on front of unit and I would not have wasted $207.
Outstanding customer service, we will definitely be using them in the future for any plumbing needs. Can’t thank them enough!
Extremely knowledgeable and very helpful. The team was excellent. The job was completed in 1 day with a great team. Very expressive.
Daniel Perez was great in coming out to check the problem I had with a water leak from my air conditioner line. His recommendation was correct.
Great and informative service while I was in a bind without a functioning water heater.
Plumbing Express is my go-to plumbing support team. They have fair pricing, well-vetted technicians, and a truly exceptional scheduling system. Rod, my technician, was the best. He quickly assessed the problem and gave a fair estimate, working hard to keep to the schedule. He even brought Josh along on the day of service, and the two of them worked well together. They addressed the bathtub drain repair with expertise and caused the least sheetrock damage. It was difficult to replace the broken pipe and get to the upstairs drain, but together they made it a success.
Daniel did a great job and was very professional during his service call last week!
Rod and Josh did an awesome job taking care of my clogged sinks. Knowledgable, professional and great to work with - I really appreciated their help today and would highly recommend them and Plumbing Express!
Daniel was excellent. The work he did was simply superb. I highly recommend your company and hopefully Daniel will get more and more work
Dylan from Plumbing Express came over and replaced our garbage disposal for us. It was older, had a massive leak, and needed to be replaced. He did a great job and was in and out in about 30 minutes! I also asked him to check out a potential leak I had been hearing in my ceiling. He used a thermal camera to investigate and was very honest and upfront about what he found. Rather than immediately cutting into the drywall to confirm something uncertain, he explained that the sound could simply be pipes expanding and that opening the wall might be unnecessary. He recommended monitoring the area and waiting to see if a wet spot appears, which would clearly indicate an actual leak. I really appreciated that he didn’t try to upsell or push unnecessary work. Overall, great service and a great guy. They will definitely be our go-to plumbing service from now on.
Once again we had some problems under our kitchen sink so we called Plumbing Express who were able to get us on their schedule pretty quickly after these storms Tim Robinson came out to do the job. Tim has been to our house for a number of different plumbing problems. He is personable & professional. As usual he did a great job even though this particular problem turned out to be far more difficult than anyone had expected. As frustrating as it was, Tim worked through it until he finished the job. We can't thank him enough.
Anthony was very competent, professional and friendly. He answered all my questions throughly. Highly recommend!
Frequently Asked Questions About Rinnai Tankless Water Heaters
How long does it take for a Rinnai tankless water heater to deliver hot water?
The unit itself reaches full output in two to three seconds after the flow sensor activates. How quickly hot water arrives at your tap depends on the length of pipe between the unit and the fixture. In most Atlanta homes, a tap that is 20 to 30 feet from the unit sees hot water within 15 to 30 seconds. Installing a dedicated recirculation pump or a Rinnai Circ-Logic controller cuts that wait to near zero by keeping a small volume of warm water moving through the supply lines continuously.
What is the lifespan of a Rinnai tankless water heater?
A Rinnai unit installed by a licensed plumber and maintained on an annual schedule typically lasts 20 years or more. That compares to 8 to 12 years for most standard storage tank heaters. The heat exchanger carries a 12-year warranty from Rinnai, and parts are covered for 5 years. The biggest factor in reaching that 20-year mark is descaling. Atlanta’s water carries enough mineral content to build scale inside the heat exchanger over time. Flushing the unit once a year with a descaling solution keeps the exchanger clear and preserves rated efficiency.
Can a Rinnai tankless water heater run out of hot water?
No. Because the unit heats water as it flows rather than drawing from a stored supply, there is no tank to exhaust. As long as cold water flows in and the gas supply is active, the unit produces hot water. The practical limit is the unit’s maximum flow rate. If simultaneous demand across multiple fixtures exceeds the unit’s rated gallons per minute, output temperature drops rather than cutting off entirely. Plumbing Express sizes every unit to your home’s fixture count and typical usage pattern before recommending a model.
Does a Rinnai tankless water heater work during a power outage?
No. Rinnai residential tankless units require a 120-volt electrical connection to power the control board, igniter, and flow sensors. If the power goes out, the unit will not fire even though gas supply remains available. A standby generator that provides at least 120 volts to the unit will restore operation during an outage. If uninterrupted hot water access during power outages is a priority for your household, ask our team about compatible backup power options when you call.
Is Plumbing Express licensed and insured to install Rinnai tankless water heaters in Atlanta?
Yes. Plumbing Express holds a Georgia master plumber license and carries full general liability insurance and workers’ compensation coverage. Every technician is a background-checked W-2 employee, not a subcontractor. We pull permits where local jurisdictions require them and ensure every installation meets current Georgia plumbing and gas codes.
Our Service Areas
Serving Metro Atlanta, North Georgia, and Surrounding Communities
Plumbing Express provides plumbing, repiping, water heater, and drain cleaning services to homeowners across Metro Atlanta and North Georgia. Our licensed plumbers know the plumbing systems in this region, from aging polybutylene pipes in 1980s subdivisions to clay sewer lines in older neighborhoods.
We serve the following counties and communities:
Don’t see your city listed? We likely serve your area too. Visit our full service area page or call (678) 439-9540 to confirm availability at your address.
Schedule Your Rinnai Tankless Water Heater Service in Atlanta, GA
Plumbing Express serves Metro Atlanta from our office at 3050 Presidential Dr #202, Atlanta, GA 30340. We have installed and serviced Rinnai tankless water heaters across the metro since 2007 and carry a 4.9-star rating across more than 1,999 verified reviews.
You can find us on Google Maps as a licensed Tankless Water Heater Installation in Atlanta, GA provider. Our team answers the phone 24 hours a day, seven days a week.
Call (678) 439-9540 or schedule online to book your installation or service visit.