The Mizudo indoor tankless water heater is a compact, efficient solution for small homes, apartments, and cabins, delivering 4.3 GPM of continuous hot water with 100,000 BTU. Its sleek design includes a touch panel LED display, supports simultaneous water supply for
2 to 3 water points, and precise temperature control. The heater features an oxygen-free copper heat exchanger for durability, and a high-speed anti-backflow fan. With over 50% space savings compared to traditional heaters. Specifications include 120V power, and wall-mounted installation.
What our Experts Think
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Reliable on‑demand hot water supply
The Mizudo 4.3 GPM Tankless Water Heater Indoor Natural Gas 100,000 BTU 120 V New – FDG‑CS100W‑NG delivers continuous hot water without a storage tank, eliminating standby heat loss and providing instant supply as needed. Its 100,000 BTU output and up to ~4.3 GPM flow can support multiple fixtures (2–3) at once, depending on inlet water temperature.
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Compact, space‑saving design
Wall‑mounted and non‑condensing at approximately 20.5″ × 13″ × 7″, it frees up space compared with traditional tank heaters and is suitable for apartments, tiny homes, or residential indoor use.
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Efficient & certified performance
With a UEF over 0.81 and CSA safety certification, this unit balances stable hot water delivery with reasonable energy efficiency for everyday household needs.
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Precise temperature control
The LED touch panel allows settings from ~95 °F to 149 °F with accurate control and minimal fluctuation, improving comfort and consistency.
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Durable build with protection features
Built‑in protections (anti‑scale, overheat, dry combustion, flame failure) and oxygen‑free copper heat transfer enhance reliability and longevity compared with many traditional tank systems.
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Easy plumbing compatibility
Standard ¾″ NPT water and gas connections and 3″ power venting make it compatible with typical indoor installations, though professional installation is strongly recommended for safety and code compliance.
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Best for moderate residential use
Experts recommend this heater for small‑to‑medium homes or apartments where reliable, continuous hot water is needed and space efficiency, simpler plumbing setup, and consistent performance are priorities.
Q&A
Q: What is the Mizudo FDG‑CS100W‑NG 4.3 GPM Natural Gas Tankless Water Heater?
A: A natural gas‑powered indoor tankless water heater that provides on‑demand hot water without a storage tank, designed for residential indoor installations.
Q: How much hot water does it deliver?
A: Up to 4.3 gallons per minute (GPM) of continuous hot water at a 100,000 BTU rating, suitable for supplying 2–3 fixtures simultaneously, depending on inlet water temperature.
Q: Where can it be installed?
A: Installed indoor‑mounted on a wall, compatible with 3/4″ NPT gas and water connections and a 3″ power vent system for proper venting.
Q: How efficient is this heater?
A: It features a Uniform Energy Factor (UEF) over 0.81, meaning efficient gas usage and reduced energy waste compared with traditional tank water heaters.
Q: How is the temperature controlled?
A: Offers precise digital temperature control with a range of about 95 °F–149 °F, and an LED touch panel for easy adjustment.
Q: What safety and durability features are included?
A: Includes anti‑scale/anti‑freeze protection, overheat shut‑off, dry combustion safety, leakage protection, and accidental flame failure protection—and is CSA certified for safety compliance.
Q: What size and connections does it use?
A: Dimensions approx. 20.5″ × 13″ × 7″, with 3/4″ NPT gas and water connections and supports standard residential water pressure (15‑150 PSI).
Q: Why choose this model?
A: Compact and efficient, it saves space vs. traditional tank heaters, delivers endless hot water on demand, and supports multiple outlets for everyday household use.
Maintenance Tips
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Annual Flush/Descale: Flush the heat exchanger yearly with a descaling solution to prevent mineral buildup and keep water flow and heating efficiency optimal (especially in hard‑water areas).
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Clean Inlet Screen: Periodically check and rinse the cold‑water inlet filter to remove debris and protect internal components.
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Inspect Gas & Water Connections: Check for leaks, corrosion, or loose fittings on gas and water lines; tighten or service as needed for safe, efficient operation.
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Vent & Air Intake Check: Ensure the venting system and air intake are unobstructed for proper combustion and exhaust.
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Wipe Exterior & Controls: Clean the exterior with a soft cloth and monitor the LED display for error codes or irregularities; address issues promptly.
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Professional Annual Service: Have a qualified technician inspect and service the unit yearly for safety checks, gas pressure testing, and optimal performance.
