When it comes to gas tankless water heaters, one brand consistently stands out: Rinnai. Known for its reliability, efficiency, and advanced engineering, Rinnai has become a trusted name for homeowners who want endless hot water without the waste of a traditional tank system.
In this guide, we’ll take an in-depth look at the best Rinnai gas tankless water heaters in 2025, what makes them special, and how to choose the right model for your home. At the end, we’ll also talk about a crucial part of your plumbing system that often gets overlooked—something that could save you thousands in repairs.
Why Choose Rinnai for a Gas Tankless Water Heater?
Rinnai has been producing high-quality heating products for nearly a century, and their gas tankless water heaters are known for:
- Exceptional durability: Built to last 20 years or more with proper care.
- High efficiency: ENERGY STAR® certified models reduce utility costs.
- Advanced technology: Features like Wi-Fi connectivity, recirculation systems, and precise temperature control.
- Wide range of models: Options for small apartments up to large family homes.
Rinnai’s focus on quality means fewer breakdowns, better performance, and strong warranties compared to many competitors.
Best Overall: Rinnai RU199iN Super High Efficiency Plus
The RU199iN is the flagship of Rinnai’s gas tankless lineup. It’s a condensing unit designed for high-demand households.
- Flow rate: Up to 11 gallons per minute (GPM) – runs multiple showers and appliances at once.
- Fuel type: Natural gas.
- Efficiency: ENERGY STAR® certified, ultra-low NOx emissions.
- Design: Compact, wall-mounted, and built with premium materials.
- Recirculation: Compatible with Rinnai’s Circ-Logic technology for faster hot water delivery.
This model is perfect for large homes where hot water demand is constant and high.
Best for Medium Homes: Rinnai RL94iN
The RL94iN is slightly smaller in capacity but still powerful enough for most households.
- Flow rate: 9.4 GPM.
- Fuel type: Natural gas.
- Efficiency: Non-condensing but still highly efficient.
- Ideal for: Homes with two to three bathrooms.
If you want Rinnai quality without the price of the RU series, the RL94iN is a great pick.
Best for Small Homes or Apartments: Rinnai V65iN
The V65iN is compact, affordable, and efficient, making it perfect for smaller households.
- Flow rate: 6.5 GPM.
- Fuel type: Natural gas.
- Efficiency: High efficiency with a smaller footprint.
- Ideal for: Homes or apartments with one to two bathrooms.
Best Outdoor Option: Rinnai RL75eN
If you prefer to save indoor space, the RL75eN is an outdoor model built to handle the elements.
- Flow rate: 7.5 GPM.
- Weather resistance: Protective casing and freeze protection.
- Ideal for: Mild to cold climates where indoor space is limited.
How to Choose the Right Rinnai Model
When selecting your Rinnai gas tankless water heater, consider:
- Flow rate (GPM): Match this to your household’s peak demand.
- Fuel type: Most Rinnai units use natural gas, but propane versions are available.
- Indoor vs. Outdoor: Choose based on available space and climate.
- Efficiency rating: Condensing models are more efficient but often cost more upfront.
Pro Tip: Have a licensed installer check your gas line capacity before buying—high-flow models may need larger lines than older systems.
Installation & Maintenance Tips
Professional installation is recommended for all Rinnai gas units. Proper venting, gas line sizing, and water connections are critical for safety and performance. Once installed, maintain your system by:
- Flushing annually to remove mineral deposits.
- Cleaning filters if your unit has them.
- Inspecting venting and water lines regularly.
Following Rinnai’s maintenance guidelines will keep your heater running efficiently for decades.
The Forgotten Side of Your Plumbing System
While your Rinnai gas tankless water heater ensures endless hot water, what happens after that water leaves your drains is just as important. If your home has a septic system, neglecting it can lead to slow drains, foul odors, and expensive backups.
Many homeowners forget about septic care until a costly problem arises. Preventive maintenance is far cheaper than emergency repairs.
SEPTIFIX – Protect Your Septic System
SEPTIFIX is the #1 septic tank treatment in the US. These flushable tablets release oxygen and beneficial bacteria that break down waste, sludge, and grease while neutralizing odors.
Benefits include:
- Removes foul odors in just days.
- Prevents costly pump-outs and system failures.
- Safe for all septic systems and eco-friendly.
- Easy to use—flush one tablet per month.
By pairing your new Rinnai heater with regular SEPTIFIX treatment, you ensure your whole plumbing system stays healthy.
Final Thoughts
In 2025, Rinnai remains the gold standard for gas tankless water heaters. The RU199iN is perfect for large households, while the RL94iN, V65iN, and RL75eN cover a range of needs from medium homes to outdoor installations.
Whichever model you choose, remember that hot water is only half the equation—keeping your septic system healthy ensures your home’s comfort and functionality for years to come.
Order SEPTIFIX Today – Keep Your Septic Tank in Top Condition
Endless hot water from Rinnai, plus a healthy septic system? That’s a winning combination for any home.