Rheem 8.4 GPM Low NOx Tankless Water Heater Review

Product Name:8.4 GPM Low NOx Direct Vent Tankless Natural Gas Water Heater
Power Source:Natural Gas
Use Type:Indoor
Capacity:8.4 GPM
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The Quick Review

Considered the gold standard in tankless water heaters, the Rheem 8.4 gallon per minute tankless unit is one of the most popular in the United States and a best-seller on Amazon. And that’s no surprise: with the industry leading warranty, 94% efficiency and powered by natural gas, this unit is the safest bet for anyone looking to replace their conventional electric tank based water heater with a tankless inline one.

We’d like to thank Sparky Channel for a great overview of the product:


With the ability to heat 8.4 gallons of water per minute, this water heater can simultaneously heat 2 showers and an appliance. For the average house smaller than 3000 sq ft, this will be the ideal capacity for you. For houses with 3 bathrooms or more, or want to run more hot water simultaneously, you may want to check out Rheem’s 9.5 GPM tankless water heater.


Since this tankless water heater requires a gas line hook up, you will require professional installation. We do not recommend an amateur attempt to install this unit as working with gas lines can be very dangerous. That said, for a professional, this installation is quite straight forward and shouldn’t run up a large labor bill. Many individuals on Amazon has reported that they were able to install it themselves with ease.


This is a product for people who are looking for long-term value and a high quality tankless water heater that will last. The product comes with a 10 year warranty on the heat exchanger and are known to last much longer than this. While there are both more expensive and less expensive units available on the market, The Rheem 8.4 GPM Tankless Water Heater is one of the best value units in the 8.4 GPM capacity category on natural gas.

Over the long run, the extreme efficiency of this unit using natural gas will be much less expensive than electric hot water tanks.

The Misses

Most tankless water heaters take a while for the water to heat up when you turn on the faucets, and this unit is no exception. It can take up to 20 seconds (in the winter) for the water to heat up, which is slower than conventional electric water tanks. For a unit of this quality, we would expect them to innovate in this area.

The unit produces more noise than is to be expected as well. Be sure to install it in an isolated area like the garage or in a sound resistant utility room. Again, much different than an electric tank-based water heater, which makes virtually no noise at all.

There have also been some customers who have reported receiving a faulty unit and having to wait weeks for the warranty process to complete and the new unit shipped out. Fortunately, this was a very small percentage of overall reviews on the product. The majority of purchasers give this product 5 stars or more on Amazon.

Our Recommendation

We definitely recommend this product for any house with 3 bathrooms or less and can stand not to run all appliances and showers at once. Be sure to check the price to see if a discount is available today.

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