Rheem RTG-64XLP Outdoor Propane Tankless Water Heater Review

If you're in the market for a tankless water heater, here is a good recommendation for you:

Rheem RTG-64XLN 6.4 GPM Low NOx Outdoor Tankless Natural Gas Water Heater

It's a mouthful, but don't be intimidated. Every number and description has a purpose, and by the time I'm finished reviewing this product, you'll understand what each one means.

Let's take a closer look at the RTG-64XLN.


This is one of the most important considerations when buying a tankless water heater. What kind of technical details does it have? In order not to miss anything, let's examine them one at a time.

  • Flow rate: Through the official flow rate of the RTG-64XLP is 6.4 gallons per minute (gpm), customers have reported fluctuations depending on things like altitude, outdoor temperature and the number of appliances demanding water. Your gpm might be anywhere from 5-7gpm.
  • Power: It needs at least 150,000 BTUs, so plan accordingly.
  • Size: The RTG-64XLP measures 14 x 10 x 26" and clocks in at 38 pounds. It isn't the lightest unit on the market, but it's far from the heaviest, too.


The RTG-64XLP is a natural gas unit, so you'll need to keep an eye on it to ensure that the burners are always working properly and the vents are always fully functional.

When used according to the manual, however, it poses no more danger than a traditional stove top with a pilot light.

Actually, it probably poses less danger because of the unit's special "low NOx" guarantee.

It's designed to form, burn and pump less gasses and fumes than other models, and those that can't be avoided are passed harmlessly through the vents and into the atmosphere.

Please note that the RTG-64XLP must be installed outside. This is because of the aforementioned venting system.

If placed inside, especially in an enclosed space like a garage, the fumes will build up and pose a health hazard. It needs to be outside where the fumes can pass into fresh air.

Heat Output and Flow

As I mentioned previously, the flow rate of the RTG-64XLP will depend on various factors both inside and outside your home. Generally speaking, however, you can expect to receive at least 5 gpm.

It's also doubtful that you'll notice the difference between 6.4 and 6.8 gpm, so flow rate shouldn't be a big concern in your final purchase decision. It's solid.

As for heat, the normal maximum of the RTG-64XLP is 140°F, but it can be programmed to reach 180° if need be. This is more than enough to enjoy a hot bath or really scald your pots and pans.

One thing you should be aware of is that the RTG-64XLP doesn't kick in until the flow rate reaches a minimum of .26 gpm. This isn't a problem for most homeowners, but it's a number to consider along with the rest.


You'll find the RTG-64XLP relatively easy to install. Again, it must be done outdoors, but it involves the same wires and circuits as an indoor unit, so there will be no surprises there.

Here are just a few of the tools and supplies you may need for installation:

  • Valves
  • Vents
  • Water heater connector
  • Ground lines
  • Amp breakers
  • Pipe cover

A remote controller and 10-foot thermostat wire are included with your purchase, so you won't have to worry about those.

If you have any questions or concerns about installing your unit, talk to a trained Rheem technician.

General Use

I've already spoken a little about the pros and cons of this unit, but for clarity's sake, let me spell them out. You'll want all the information on hand when you make the final decision about whether or not the RTG-64XLP is the right tankless water heater for you.


  • Solid, hard-working natural gas unit
  • In the middle tier of affordability
  • Low NOx


  • Must be installed outdoors
  • Flow rate might change with simultaneous usage
  • Minimum flow rate of .26 gpm

What's the bottom line?

Do you worry about the fumes of a natural gas tankless water heater? Then the RTG-64XLP is the perfect choice for you. Out of five stars, I'd give it a solid four; while it does have certain components you'll need to keep an eye on, it's no more work than your regular water tank used to be.

You don't have to take the word of a stranger on the Internet, however. Look up the Rheem RTG-64XLP on Amazon and see for yourself how much customers love it!

  1. What keeps the water lines outside from freezing

  2. […] Read detailed review on Rheem RTG 64XLP […]

Enable registration in settings - general
Compare items
  • Total (0)