When a tankless water heater fails to ignite, of course your water heater won’t work. So what causes an ignition failure? It’s usually one of these reasons:

  • gas supply interruption
  • electrical outage
  • wiring loose
  • electrode loose
  • air flow insufficient
  • ignition plug or burner with debris
  • flow rate too low
  • ignition switch failure
  • high limit switch failure
  • electronic board faulty

Tankless Water Heater Ignition Failure Error Codes

tankless water heater ignition failure error code 11

How do you know if the reason you’re not getting hot water from your tankless water heater is because of ignition failure? Newer tankless models include self diagnostics. So as long as the electrical is working, they will display error codes indicating the specific problem.

Error code 11 will be displayed for an ignition failure on these tankless brands:

  • Noritz
  • Rinnai
  • Rheem
  • Takagi

A whole-house Navien tankless water heater will show error codes E003, E012 or E110.

Try These Fixits First

We’re here to help, of course. But you could first see if these simple solutions work. If none works, please call us!

Are You Sure You have Gas?

Even smart people sometimes forget to check that they have enough propane (if that’s their fuel source). Often the water heater is the FIRST to run out so just because your stove gas burner still lights up, it does not mean your water heater is getting its gas supply. Likewise, if your home has natural gas, be sure you’ve paid your gas bill.

Make sure the gas valve is still open.

Make sure the gas valve is in the “open” position. This diagram shows a Noritz tankless gas valve open.

Is Your Electricity Working?

All tankless water heaters need electricity, even the gas fueled models. That’s because they all contain electronic panels that indicate error codes, temperature gauges, and electronic ignitions. So if electricity is working in other parts of the house, check the circuit breaker that corresponds to your tankless water heater and make sure it’s still switched to the on position.

If you don’t know WHICH circuit breaker goes to the water heater, look for one in the “off” position. Then BEFORE turning it back on again, you’ll want to recall if any other appliances went off at the same time as the water heater (meaning they were all on the same circuit breaker). Turn all those appliances off before flipping the circuit breaker back on again.

Does the Circuit Breaker to the Tankless Water Heater Continually Trip?

When you turn the circuit breaker back on again, does that fix the problem with the water heater? If so, terrific. But if the circuit breaker continues to trip it could mean you have too many appliances running simultaneously on the same circuit breaker. Overloaded circuit breakers could cause a fire if they fail to trip off. If that circuit breaker is NOT overloaded and continues to trip, then turn that circuit breaker off and call an electrician. That circuit likely has an electrical short. Electricity is nothing for an amateur to fool with.

Power Outage Means No Hot Water From a Tankless Water Heater

And if you have a power outage, of course your tankless water heater will not work because it cannot ignite. That is a down-side to a tankless water heater. (A conventional tank-style water heater of course can continue to supply at least the warm water sitting in the tank.)

If Your Tankless Water Heater is Electric, Check the High-Limit Switch

When a high-limit switch trips, the water heater shuts off. It can happen even in the middle of a hot shower. It’s there to protect you by preventing the water from becoming too hot. So you want to discover what’s causing the switch to trip. It you have the temperature set too high, try turning the temperature control lower. Then reset it by turning the power off and turning it back on. If that fixes the problem, great! But if the high-limit switch continually trips, it usually means either:

  • a faulty thermostat that needs to be replaced
  • malfunctioning high-limit switch needs replacement
  • a short in the heating element that needs professional replacement
  • or loose wiring that needs reconnection

Next, Check for Loose Wiring and Electrodes

Whether you have an electric or gas tankless water heater, you’ll still have wiring and electrodes. Check all visible wiring and electrodes to see if any are loose and reconnect them.

Air Flow and Vents Unobstructed?

Clean air filters and check that vents are not obstructed.

Flow Rate Too Low?

All tankless water heaters have a minimum flow rate requirement. Most newer models require half gallon per minute to fire up and older models require three quarters of a gallon per minute. 

Combine that flow rate requirement with water-conserving shower heads and you may be taking cold showers. It’s a delicate balance between saving water and meeting the water flow rate requirement for tankless water heater.

Try these, to fix a flow rate issue:

  • clean aerators on shower heads and faucets
  • clean out the water inlet filter
  • increase the flow rate (if possible)

Rheem Displays Error Code P1 for Low Flow Rate

Some tankless brands, like Rheem, will display a separate error code if it detects a flow rate that’s too low to fire up the unit. Rheem displays Error Code P1.

When These Simple Remedies Fail to Ignite Your Tankless, It’s Usually a Sensor or Electronics Failure

We have the tools and experience to quickly identify failed sensors and circuit boards. If it’s cost-effective to repair your tankless (and its not reaching its 20 year life expectancy), we’re the most qualified plumbers to repair it! If it is reaching its end of life, we’re also the most affordable plumber to replace it!

In fact, we guarantee you the best price! We beat even big box store prices on water heaters!

And we are the area’s leading water heater experts. So call us! We’re here to help.

Need Other Reasons to Call Us for Water Heater and Plumbing Needs?

We are locally owned and operated, serving and trusted by our neighbors in Fallbrook, Bonsall, Vista, Oceanside and Temecula for over 30 years. Plus, we:

  • guarantee your satisfaction
  • have the highest all five-star customer satisfaction rating (read some of our reviews here)
  • deliver the best price for the highest quality service
  • guarantee our workmanship for ten years (products carry their own warranties)
  • handle all product registrations and warranties for you
  • are the most affordable plumber

Other Reasons Tankless Water Heater Not Operating as Expected

You can read about other reasons for the most typical tankless water heating issues here. We provide more tips to remedy those problems too.

Sudden Spike of Cold Water While Taking a Hot Shower?

One of the biggest complaints from tankless water heater customers is a getting sudden spike of cold water in the midst of a hot shower. It usually happens when a second person jumps in the shower soon after the first. You can read more about the cold water burst when using a tankless water here.

The main reason for the cold water burst during a shower for the second person, however, is NOT a problem with the tankless unit. It’s simply that the second person initially receives residual hot water left in the pipes from the first person’s shower. The blast of cold water happens when that residual hot water is exhausted. Then cold water comes out while of the pipes until the newly demanded hot water to reach the shower again. How long it takes for hot water to once again come out of the shower depends on how far away that shower is from the tankless water heater.

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