Our readers keep the lights on and my morning glass full of iced black tea. As an Amazon Associate, I earn from qualifying purchases.10 Best 50 Gallon Gas Water Heater | Skip The Cold Sandwich

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The Rinnai RX199iN is a condensing unit that achieves a UEF of .98 — the highest efficiency tier available in residential tankless water heaters. With an 11.1 GPM flow rate at a 199,000 BTU input, this unit can handle up to seven fixtures simultaneously, making it the best fit for large families or homes with multiple full bathrooms. Its condensing design captures heat from exhaust gases before venting them through inexpensive Schedule 40 PVC pipe, which also simplifies installation compared to Category III venting.

The Smart Sense gas control system allows the RX199iN to automatically detect and switch between natural gas and propane right through the settings menu — no conversion kit required. The Versa Vent system means this same unit can be installed indoors or outdoors, cutting down on inventory confusion. Users consistently praise the whisper-quiet operation and the ability to run several showers, the dishwasher, and washing machine without any temperature fluctuation once the water reaches the set point.

One real-world consideration is the delay in hot water reaching distant faucets, which is common in all tankless designs. Some users in larger homes have paired this unit with an external recirculation pump or the optional Controlr Wi-Fi module to reduce wait time. The Rinnai Central app is rated well for setup and diagnostics, but experienced DIYers report that the onboard panel is fully capable without the phone connection.

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The CX199iN is Rinnai’s commercial-grade offering that carries the same 11.1 GPM and 199,000 BTU backbone as the RX199iN but adds higher duty-cycle components to handle more sustained demand. Its 97% thermal efficiency is nearly identical to the residential flagship, but the commercial designation makes it a stronger choice for homes with exceptionally high hot water usage or those adding a separate living unit, like an in-law suite or rental apartment.

Installation flexibility continues with the Versa Vent system and the Smart Sense fuel detection, allowing indoor or outdoor placement with either natural gas or propane. The CX199iN also offers an optional recirculation conversion kit, which can be installed to provide near-instant hot water at the furthest tap. Users upgrading from older Rinnai units (which can be 18+ years old) report a noticeable improvement in speed to temperature and significantly quieter operation.

The beefed-up construction is reflected in the slightly larger footprint — it is taller than some residential models and may require gas line and plumbing adjustments. While this unit is pricier than most residential options, owners of large households (8 or more people) report that the gas savings from the high efficiency offset the cost within the first year. A handful of users caution that professional installation is a must, as the gas supply line needs to be at least 3/4 inch to feed the burner properly.

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The RE199iN is Rinnai’s non-condensing powerhouse that delivers an impressive 9.8 GPM — enough to supply a whole house with 3-4 bathrooms simultaneously. It uses standard Category III venting (stainless steel) instead of the PVC used by condensing units, but its upfront cost is significantly lower, making it a strong mid-range option for buyers who want Rinnai’s reliability without the premium of a condensing model. The 15-year limited warranty on the heat exchanger gives long-term peace of mind for this investment.

Users consistently report smooth installations when replacing older Rinnai units because the footprint and venting requirements are often compatible with the existing setup. The LED diagnostic display and service reminders help with maintenance, though the unit does not have built-in recirculation. For large families running multiple showers and appliances at once, this unit holds temperature well — owners note no cold bursts as long as the total GPM demand stays under the 9.8 limit.

The trade-off for the lower purchase price is efficiency: non-condensing models vent hotter exhaust, meaning some heat goes up the flue instead of into the water. Annual energy costs will be slightly higher compared to a UEF .98 condensing unit. Some users also mention the exhaust fan is noticeably louder than the newer condensing Rinnai units, so consider placement near bedrooms if noise sensitivity is a factor.

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What sets the A. O. Smith ATI-310CX3 apart is its X3 Scale Prevention Technology, which eliminates the need for annual descaling and isolation valves — a major pain point for tankless owners in hard water regions. With an 8.0 GPM flow rate powered by a 190,000 BTU commercial-grade copper heat exchanger, this unit is well-suited for 2-3 bathroom homes. The copper heat exchanger delivers 25x better heat transfer compared to steel, translating to faster heat-up and stable water temperatures.

The unit runs quietly, as multiple verified purchasers note, and includes a propane conversion kit right in the box — a convenience many competing brands charge extra for. The integrated temperature controls and advanced diagnostics panel make setup straightforward for a qualified technician. Users report professional installations taking less than half a day, with plumbers praising the build quality and compact 20.5-inch height that fits tight spaces.

One nuance mentioned by users in warmer climates: if incoming water is already above 80°F, some shower balancing valves can trick the unit into shutting off because the internal thermostat sees a high inlet temperature. This is solved with a simple cold water restrictor, but it is worth knowing before installation. The warranty is solid at 15 years on the heat exchanger for residential use, matching Rinnai’s standard.

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The Rheem RTG-84XLN-3 offers an 8.4 GPM flow rate with 180,000 BTU input in an outdoor-rated cabinet, making it a strong choice for homeowners who want to avoid cutting vents through their roof or sidewall. This non-condensing unit is designed to mount on an exterior wall, eliminating the need for Category III venting entirely and simplifying installation. Its compact 20.75-inch height and 39.25-pound weight make it one of the lighter and smaller units in its flow class.

Rheem’s Hot-Start programming is built in to prevent the cold water sandwich effect commonly experienced with tankless heaters when there are back-to-back showers. Verified purchasers running this unit in two-to-three-bathroom homes consistently report that it keeps up without noticeable temperature drops when the washing machine and shower run concurrently. The altitude adjustment feature is also appreciated by users in mountain communities who found that earlier units struggled at high elevation.

Because this is an outdoor model, you must protect it from direct exposure to rain and snow — it should be installed under an eave or in a sheltered spot. Some users note that the water takes slightly longer to heat up compared to a tank-style heater (typical for all tankless units), but once the burner engages, the hot water is continuous. The 1-year labor, 15-year heat exchanger, and 5-year parts warranty provide solid coverage for the mid-range price point.

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The RTG-84DVLP-3 is the liquid propane sibling of the outdoor model above, designed specifically for indoor installation. Its 8.4 GPM capacity at 180,000 BTU is the same power plant, making it equally capable of handling 2-3 bathroom homes with propane as the fuel source. The non-condensing design requires Category III venting, but users appreciate that Rheem’s venting kits are readily available and straightforward for qualified installers.

Customer feedback highlights the transition from an old tank-style water heater to this Rheem as a major convenience upgrade — no more scheduling showers around recovery time. The Hot-Start feature is specifically called out as effective at eliminating cold temperature fluctuations during back-to-back uses. Owners of the propane version also note that the gas gauge on their tank barely moves, indicating efficient combustion even after installing the unit in mid-sized homes.

There are mixed reviews on long-term reliability, with a few users reporting error codes and premature failure within 6 months. The stainless steel heat exchanger carries a 15-year warranty for residential use, which provides some protection against manufacturing defects. Consistent professional installation and proper gas line sizing (3/4 inch minimum) are critical to avoiding operational issues.

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The RTG-84XLP-3 fills the specific niche of an outdoor propane tankless water heater, making it a favorite for cabins, rural homes, and properties where running a vent through the wall is impractical. It shares the same 8.4 GPM / 180,000 BTU internal specs as its indoor counterpart but in a weather-resistant outdoor cabinet that weighs just 39.25 pounds. Eliminating the venting requirement reduces installation complexity and cost significantly.

Users report that the unit provides excellent hot water supply for 2-3 bathroom homes, and the outdoor placement frees up valuable floor space that would otherwise be occupied by a tank. The unit includes Rheem’s Hot-Start programming and altitude adjustment, both of which are appreciated by owners. Some verified purchasers note that adding an external recirculation pump and timer dramatically reduces water waste while waiting for hot water in larger homes.

However, a notable subset of reviewers report persistent Error Code 11 (ignition failure) on this specific model, with some users unable to resolve the issue even after replacing the propane regulator. This appears to be a batch-specific problem, as the majority of reviews are positive, but it is a risk to consider. If you are in a remote or rural area, make sure your propane tank has a high-capacity regulator (not a standard BBQ regulator) to supply enough gas pressure for the 180,000 BTU burner.

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The RX130iN is the smaller sibling in Rinnai’s condensing lineup, delivering 7.1 GPM at 130,000 BTU with an impressive UEF of .97. This unit is ideal for homes with 2-3 bathrooms and moderate simultaneous demand, or for buyers who want Rinnai’s top-tier efficiency at a more accessible price than the big 11.1 GPM models. Its lower BTU rating means it is best suited to warmer climates where groundwater temperatures are above 50°F — in cold northern regions, the flow rate will be effectively reduced.

Like the larger RX199iN, this unit uses Versa Vent technology for indoor or outdoor installation and Smart Sense gas control for automatic fuel-type detection. Users who installed this in alpine climates report it handles two showers plus a dishwasher in 10°F weather without issues, as long as the incoming water temperature is accounted for. The Quick Flush feature simplifies maintenance, and the compact size (19 x 31 inches) makes it easy to mount in tight utility spaces.

A few users note that this unit takes about 50% longer to bring water up to temperature compared to their previous tankless heater, which is consistent with the lower BTU rating. The trade-off is exceptional efficiency that translates to noticeably lower gas bills. Professional installation is recommended, especially if you need to upgrade the gas line to 3/4 inch. The unit does not include flush valves or a pressure relief valve in the box, so budget an extra for these essentials.

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The RTG-70DVLN-3 is Rheem’s entry-level 7.0 GPM indoor natural gas tankless unit. At 160,000 BTU, it provides enough hot water for 2-3 bathroom homes with moderate simultaneous usage — think two showers running with the dishwasher. This is a non-condensing model that requires Category III venting, but its lower upfront cost makes it an attractive option for homeowners who want to go tankless without spending into the premium tier.

Users consistently praise this unit for its reliable performance with older, undersized piping — a common pain point in older homes where upgrading the plumbing is prohibitively expensive. The Hot-Start programming prevents the cold water sandwich, and the altitude adjustment works well for homes above 5,000 feet. Verified purchasers report smooth DIY installations when they follow Rheem’s venting guidelines carefully, though professional installation is always recommended for gas appliances.

The main complaint across reviews is the time it takes for hot water to reach the faucet, with some users noting a 30-60 second delay depending on the distance from the heater to the fixture. This is inherent to all tankless designs, but it is more noticeable with the 7.0 GPM unit when the flow rate is pushed near its limit. The warranty package (1 year labor, 15 year heat exchanger, 5 year parts) matches the industry standard and provides adequate protection for the mid-range price.

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The RTG-70DVLP-3 is the propane version of the entry-level Rheem, offering the same 7.0 GPM at 160,000 BTU in an indoor-rated cabinet for homes using liquid propane. It fills the same role — providing endless hot water for a 2-3 bathroom home at a budget-friendly entry point — but with the fuel flexibility needed for properties without natural gas hookups. Like the natural gas sibling, it is a non-condensing design requiring Category III venting.

DIY-installing users have reported success using Rheem’s venting kit and connecting to a 100-pound propane tank with a 3/4-inch black iron pipe and a high-quality regulator. One family of six (two adults, four children with long showers) reported that a 100-pound tank lasted about a month, which is reasonable for a 7.0 GPM unit. The Hot-Start programming again helps prevent cold bursts during back-to-back showers, a common concern for tankless new converts.

However, this model has a higher rate of critical negative reviews than its natural gas counterpart. Complaints include ignition failures, loud operation, and what one reviewer called “cold spots” throughout the water flow. Some of these issues appear to be linked to insufficient gas line sizing or incorrect regulators — using a standard BBQ regulator on a 160,000 BTU unit will cause starved flow and ignition problems. If you choose this unit, ensure your plumber installs a house-type high-capacity regulator and a proper 3/4-inch gas line.