Rinnai error codes we see most
Rinnai units show a code on the controller when something's wrong. Codes vary by model, but some of the most common are:
10 — air supply or exhaust blockage. Often debris in the vent or intake.
11 — no ignition. Can point to gas supply, an igniter or a closed gas valve.
12 — flame failure. Often a dirty flame rod, gas pressure or a burner issue.
LC — scale buildup warning on many models. Time for a flush.
A code is a starting point, not a diagnosis. Write down the exact code and your model number, don't keep resetting the unit, and call us. Smell gas? Leave the house and call Dominion Energy at 800-815-0083 or 911.
Why we recommend Rinnai
Rinnai is our go-to tankless brand. We choose the model based on how many showers and appliances you run at once and how much the incoming water needs to be heated, then plan the gas line, venting and service access so it's installed right from day one.
Sized for your household — in every season
A tankless heater never runs out the way a tank does, but it has a maximum flow. Incoming water is colder in January than in July, so a unit that keeps up in summer can fall short in winter if it's undersized. We size for your coldest month and busiest morning. Want hot water to reach distant taps faster? Ask about a recirculation option.
Switching from a tank? See our tankless installation page for what's involved. Prefer a simple tank swap? See A.O. Smith.
What a Rinnai flush involves
Minerals in the water gradually coat the inside of the heat exchanger, which cuts efficiency and can trigger error codes. During a flush, your plumber shuts off the unit, uses the service valves to isolate it and circulates a descaling solution through the heat exchanger, then rinses it, cleans the inlet filter and checks operation.
No service valves on your unit? We can add them, which makes every future flush quicker. If your Rinnai is showing a code or losing heat, we'll diagnose the cause first rather than assume a flush will fix it.
Warranty help
Keep your installation paperwork — Rinnai's warranty terms are in your owner's guide and depend on your model and registration. We'll help you check what applies and tell you before any work begins.
Rinnai product warranty information
Our residential diagnostic fee is $89, waived when you go ahead with the repair at the quoted price. Pay by cash, check or card. Family-owned since 2011 with master and journeyman plumbers on staff, licensed in South Carolina (Mechanical License CLM.111515 MC).
A few common questions.
What does an "LC" code mean on my Rinnai?
On many Rinnai models, an "LC" code is a warning that scale is building up inside the heat exchanger — a sign the unit is due for a flush. Codes vary by model, so check your manual or call us with the exact code.
Why does my hot water go lukewarm when two showers are running?
Every tankless heater has a maximum flow. If two showers plus the dishwasher ask for more hot water than the unit can heat — especially in winter, when the incoming water is colder — the temperature drops. It can also be scale buildup or a failing part. Your plumber will tell you whether it's a repair or a sizing issue.
How often should my Rinnai be flushed?
We generally recommend a yearly flush, adjusted to your water and Rinnai's instructions for your model. Flushing is quoted separately from our maintenance plans.
Can I switch from a tank to a Rinnai tankless?
Yes. Switching from a tank usually means upsizing the gas line, new venting and a condensate drain — our licensed plumbers handle all of it. You'll get one firm installed price, and financing is available for qualifying installations.
