Rinnai Tankless Water Heater Problems

In this piece we specifically examine Rinnai Tankless Water Heater Problems customers typically see.  While a tankless water heater offers many strong advantages over more traditional hot water tank units, drawbacks and disadvantages exist for them too. Rinnai water heaters

Now to be sure, Rinnai tankless water heaters can be a gratifying investment in your home’s overall comfort.  They offer virtually unlimited, well-heated water for hour-long showers, many daily loads of laundry, and even outdoor hot water uses.

Please consider the following Rinnai tankless water heater problems.  Factor in these cons, limitations, drawbacks, disadvantages, and concerns  before buying.  Here’s a pretty comprehensive list.


Rinnai Tankless Water Heater Problems: High Initial Investment

High Startup Costs. While these Rinnai instant hot water, on demand units indeed offer “fast and endless” hot water, and do save you significantly on your fuel bill, they cost more to purchase, install, and to maintain. The heater purchase itself isn’t too bad, with most on demand units costing between $100 and $700. But the specialized wiring for the electric heaters, and the ventilation for the gas units can run into some big bucks to have installed.

Seeing a return on your investment can take many years. Claims abound that you can get as much a fifty percent fuel savings with Rinnai continuous flow hot water systems. If true, switching to them from the traditional water heater tank COULD be worth it over time; especially in communities with well-conditioned (soft) water, where the exchangers would tend to last longer. But recovering your investment can take as long as 22 years. That would amount to a savings of the cost of replacing two or three traditional tanks, assuming that the tankless unit would last 22 years.

Fuel Savings Estimates May Be Exaggerated. Yes, when you don’t use much water, keeping tens of gallons in reserve, and incurring the cost of keeping it hot, as is what happens in a traditional tank-based heater, costs some money. So you’d save that amount if you went tankless. But this savings may not tally to very much. Why not? Because if you’re really concerned, and are planning a trip away from home for more than a couple of days, you can just turn off the traditional heater tank until you get back. True, when you return home, you’d have to wait an hour or more for hot water. But how often would you do that anyway?  And, is this small inconvenience worth the much higher maintenance costs of a Rinnai tankless system?

Rinnai Tankless Water Heater Problems: Hot Water Delivery Issues

  • The dreaded tankless water heater pause. Since these water heaters do not activate until they sense actual water flow within, they do not keep any reservoir of hot water. Plus, there is a slight delay between the time they detect water flow, and when the heaters actually kick on. This delay may only be a second or two, but folks often site it as a drawback of no-tank water heating.
  • Output Water Temperature Can Vary with Water Pressure. In situations where water pressure input to the Rinnai may vary, such as when a toilet is flushed or a washing machine begins to fill, output water can become cooler and startlingly uncomfortable for shower takers. For absolutely consistent water temperatures, tankless water heaters require near-consistent water pressure. More traditional tank-based systems do not suffer this drawback. This problem can be minimized by purchasing a more expensive, modulated tankless heater however.
  • No Hot Water when Flow is a Trickle. You can’t draw just a trickle stream of hot water from your faucets, since the Rinnai tankless system, as do the other major brands, requires a certain minimum amount of water flowing through, in order that it may sense the water flowing, and then activates its heaters.


Rinnai Tankless Water Heater Problems: Electrical Hardships

  • Rinnai electric tankless water haters require high current wiring. Some of these units can draw a hundred amps at 220 volts (over 22 KW, as does the EcoSmart ECO 27 on demand electric water heater).   This comprises half of the maximum current allowed in a home with a typical 200 amp electric utility service. Generally, this type of wire is difficult to bend, strip, route, and handle. Further, many houses have only a 100-amp service from the utility poll in (service drop). So, upgrading to tankless would mandate a costly service drop upgrade, to 200 amps at least. Therefore installing the wiring to a tankless heater is probably best left to an electrician, unless of course, you are an electrician yourself.
  • If power fails, so also does the Rinnai electric tankless hot water heater. True of the electrically powered tankless systems, since no reserve tank of pre heated water exists in this type of heating. Further, most residential generators do not produce enough emergency power to run a tankless water heater. Gas fueled units may also require a small amount of electricity from the mains to run their control systems, and so, even certain gas units would not function during power outages. Available hot water would disappear almost immediately after turning on a connected hot water faucet. It might be wise thus, to keep a traditional gas water heater tank in the basement, connected to the plumbing system through valves, that you could engage when electricity is lost.
  • Less advantageous compared to a big hot water tank.  Further, where there’s a near-constant draw of hot water (like where women reside (*smile*), the advantage of the Rinnai tankless water heater seems less pronounced. Why?  Because drawing enough water, you would actually use the hot water before having to reheat it too many times. We’ll wait until more people experience this  technology and see how they feel about it.

Rinnai Tankless Water Heater Problems: Ongoing Support Hardships

  • Tankless Water Heaters, Different from Instant Hot Water. Tankless hot water systems, contrary to popular belief, do not give you instant hot water, at the tap. Not exactly.  While they may heat up the water that passes through them instantly and do so without any significant water reservoir, you still will not see instant at the faucet. Why? Consider that even with one of these inline water heaters, experience shows that you’ll still get that pause between turning on a hot water faucet, and actually receiving hot water; especially if the place where you’re drawing the hot water is far away from the water heater. You still must wait through the coldness for several seconds to a minute, for the heated water to travel through the pipes from the heater to your faucet.
  • Add a pump circulator for truly instant hot water.  On-demand water heaters do not solve this problem. But, installing a return pipe and a circulating pump on the other hand, does.  It gives you instant hot water, without incurring the expense of a tankless system. You need not buy tankless to get instant hot water therefore.
  • Water treatment system required for maximum life.  Among the Rinnai tankless water heater problems, is that these systems are sensitive to water impurities and minerals in the water.  So, to prevent buildup of limescale and other hard water deposits, you should install a water softening and filtration system at the cold water side of the Rinnai tankless heater.
  • High Maintenance Costs. You not only pay over twice as much initially for tankless water heaters, but these units need higher maintenance efforts than traditional tank based units. A heat exchanger comprises the heart of the on-demand system.  You must replace this every few years. This more or less depends on the condition of your water and the sort of exchanger packaged with the unit. Exchanger pipe assemblies can run a couple to several hundred dollars. So unless your need for endless hot water cancels out these draw-backs, we’d avoid tankless until prices drop a little more.

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References for Rinnai Tankless Water Heater Problems

Revision History

  • 2018-03-02: Revised the title and the tags list, and updated the content.
  • 2018-02-23: Originally published.