Rinnai Tankless Review

This review highlights the Rinnai RUR98eN but talks about many concepts common to all tankless water heaters.

When I was looking at my future home, the inspector clearly called out my water heater’s state: old and in need of replacement. It was a Bradford-White that had been heating water dutifully since 2002. I had other priorities that needed to be addressed first (says every new homeowner, 😂). I rolled the dice that things would be ok.

After three or so years, my water heater started making gurgling noises and didn’t get the water piping hot anymore. The water heater was smack dab in the middle of the house, so if it sprung a leak, the house’s damage could be extensive. It was time to bite the bullet and replace it.

Warning: On average, water heaters should be replaced around the 10-year mark (or as your warranty dictates).

I didn’t want the water heater in that central closet anymore. It was too valuable of space to not be used as a closet for other things. Getting the water heater out of the inside of the house would also reduce damage if any component failed.

Why tankless?

I’d heard a lot about tankless water heaters and thought it would be a good option for my house. I had listened to a few reasons worth mentioning here (and their relative truth in my situation).

  1. Tankless water heaters are more energy-efficient. 👍🏻
  2. Tankless water heaters supply an endless supply of hot water. 👍🏻
  3. Tankless water heaters are better for the environment. 👍🏻 👎🏻
  4. Tankless water heaters will save me money. 👎🏻 👎🏻
  5. Tankless water heaters are more space-efficient. 👍🏻

Reasons two and five sold me on the hot water heater. I wanted something that would provide a continuous stream of water and added an additional storage closet into my house.

Let’s talk about cost

Tankless water heaters don’t save you money. Tankless water heaters cost more to purchase and install, and the increased spending will not repay itself from reduced water and energy usage. A simple replacement for the tank water heater would have been $1250. How does that break down?

  • The water heater itself was about $750.
  • The plumber charged $250 for the install.
  • Additionally, the city wanted another $250 for the permit (which the plumber was required to collect).

I permit anything that has to do with 220 V electricity, water, or gas. I don’t shortcut anything in my home concerning those elements.

The tankless water heaters I was looking at was roughly 2-3x the price of the tanked counterpart. The installation cost varied wildly based on where I put the hot water heater within the home. I could not use the existing gas line as tankless water heaters need a much bigger gas line and venting system than their tanked counterparts. Keep reading to see how the installation costs and the resource savings work together to understand the true cost of ownership of the tankless water heater.

It’s all about flow

Tank water heaters have the distinct advantage that they have all of their hot water available upfront. Thus, they can dispense hot water as fast as the plumbing will push cold water into the water heater. On the other hand, tankless water heaters must heat water on demand, requiring large amounts of gas and exhaust infrastructure to run. More expensive tankless water heaters have higher heat output (BTUs) and can produce a higher flow rate (gallons per minute).

There are a few factors to consider with the tankless water heater: ambient water temperature and the number of concurrent users of hot water. Obviously, the water will be colder from the water company in a Maine winter versus a Florida summer. The water heater in Maine has to work significantly more to get the water temperature up to 120° than the same water heater in Florida. This is called temperature rise.

The more concurrent users of water within the household, the higher the flow rate will be required. In a two-bathroom house during the morning, it would not be uncommon to have two showers running and a sink or two simultaneously. Bathtubs require 4.0 GPM. Showers require 3.0 GPM. Sinks, washers, and dishwashers generally require 1.5 to 2.0 GPM. A two-bath house would likely need the flow rate of one bathtub, one shower, and one sink culminating at 8.5 gallons per minute.

Ask your local installer for specifics on ambient water temperature for your area. Also share how hot you like your water to be and how many concurrent users of hot water within the home. Over engineer a bit should preferences within the house change.

Placement Matters

Let’s take a look at the plumbing inside of a house. This house is a single level, two bath house. The water heater is currently in the center of the house. This benefits one of the bathrooms with almost instant hot water. In contrast, the kitchen, garage, and bathroom 1 have a longer wait for hot water.

Sample plumbing layout. Connection to the water company, and outdoor fixtures ignored for brevity.

I had a few options for placing a new hot water heater: in the attic above the closet, outside of bathroom one, inside of the garage, or on the exterior of the garage. Each location had its pros and cons listed below:

Gas/Power InstallVenting InstallRiskWarmup Time
Attic$$$$$$👎🏻 👎🏻🤷🏻‍♂️
Outside Bath 1$$$$$none👍🏻Bath 1: 👍🏻 Everything Else: 👎🏻
Inside Garage$$$$$👎🏻Laundry: 👍🏻 Everything Else: 👎🏻
Outside Garage$None👍🏻Everything: 👎🏻 👎🏻

I didn’t want to put the water heater in the attic. Attic access is complicated at best. In the rare event something burst, damage to my home would be even more problematic than my current situation. Running a gas line to the other side of the house was too expensive. I didn’t want to give up wall space in the garage for a hot water heater. Thus, I chose option four:

Enter recirculation

This option has the obvious downside that I’m waiting longer for hot water in every use case. Without recirculation, it takes about 5 minutes for bathroom one to reach 110 degrees F. The mitigation here is recirculation. A recirculation pump can run for that 5 minutes and make the tap instantly hot without wasting any water. Recirculation pumps do this by circulating water through a new plumbing line or with a crossover valve into the existing cold water line.

Adding a new recirculation line would’ve cost about $900, so I opted to use a crossover valve and the existing cold water line. You can see in the chart below that the hot water crosses over into the cold water line pushing the old hot water back to the water heater for reheating. This is highlighted as orange in the diagram below.

My water heater has the option to recirculate on-demand, on a schedule, or with Google Home/Alexa. I generally recirculate on-demand and with Google Home. Each bathroom has a small wireless button that tells the hot water heater to start recirculation. Shortly after the button press, I can hear the whirring of water throughout the pipes.

It’s worth noting that crossover valves have two main drawbacks. First, the cold water line may get lukewarm water when recirculation runs on a schedule. If the recirculation runs for 30 minutes, the cold water line will quickly get replaced with lukewarm water. That lukewarm water has been heated. In theory, heated water is less pure than water fresh from the water company.

The crossover valve has a thermostat inside of it to crimp close once the water temperature reaches 120 degrees. My water heater forces that the max temperature when in crossover mode must be 120 degrees.

Water heaters are smart?

Yep! I’ve more recently been using Google Home to automate various aspects of my house. Rinnai promoted Google home integration. It’s a neat feature, but the implementation is terrible and clunky to use. Once set up, I can interact with my water heater in the following manner:

Hey Google, talk to Rinnai.
-> Welcome to Rinnai. What can I help you with?
Get hot water.
-> Starting recirculation

While cool at first initially, the novelty wears off quickly. Rinnai requires voice authentication through the Google device, which often fails for me. It’s frustrating to get repeated, “since your voice wasn’t recognized, I can’t do that right now.” My voice usually does not match in the morning when I need hot water.

To make matters worse, since I can’t say, “Hey Google tell Rinnai to get hot water,” I can’t add recirculation to my good morning script which handles my alarm, morning news, lights within the house, thermostat, etc.

Unfortunately, the Google integration is nothing more than a poorly thought out marketing feature. Yes, they have Google integration, but I can’t imagine that anyone at Rinnai actually uses it, which is disappointing.

Furthermore, the software quality on this unit is low. The iPhone app is routinely buggy and error messages tend to be cryptic at best. Rinnai customer support has been helpful, however wait times on the phone are almost always exceedingly long.

Furthermore, the two plumbers I’ve had on-site to install and service the water heater didn’t have the software knowledge to configure the water heater to run as it should. While the Rinnai heats water extremely well, I can’t recommend this particular model due to many software and out of box experience issues.

Don’t forget about maintenance!

Tankless water heaters require regular maintenance for years of good performance. On average, expect to flush your water heater every 12 to 24 months based on your local water quality. One water company in the area uses snowmelt for almost pristine water. In contrast, another water company uses groundwater, which is often loaded with minerals that can be hard on a house’s plumbing.

Flushing a tankless water heater involves recirculating vinegar through the pipes to remove any calcified minerals within the heating elements. I had my first flush done by a Rinnai approved installer to ensure that the water heater was correctly installed and functioning as it should.

The good news is my water heater was performing well and not overloaded with minerals. The blue vinegar is indicative of the flushing of calcified minerals outside of the water heater. Next time, I will try the flushing process myself, as this video below was super informative on the process.

A word on saving money…

Water at the most expensive tier I’ve paid here is about $0.01 per gallon. A warmup of my shower takes about a nickel’s worth of water. Over a year I’m saving $15-$20 of water per shower. The gas usage is a bit harder for me to track so I’ve got to use averages. On average a tankless waterheater uses 78 therms less than a tank water heater. That’s about $135 dollars per year in my geography. However, I heat less water than your average household. The savings aren’t nothing, but it’s not going to recoup the few thousand more it was to install.

Have any questions? Drop them in the comments below!

Plumbing glyph icons by Vectors Market from the Noun Project

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