Best Tankless Water Heater Igniter Replacements 2026: Rinnai, Rheem, Noritz

Quick Answer: Tankless water heater igniters are not interchangeable across brands, so the “best” one depends entirely on what you own. Current Rinnai units (condensing RUC98iN and Sensei, non-condensing RL94iN) use the genuine Rinnai 105000230 Igniter Assembly (about $39–$51 at parts suppliers in October 2026); older Rinnai RL75i/RL94i-VC units need the different 105000180 instead. Rheem, Ruud, and Richmond tankless heaters shared the RTG20235C Ignitor Coil, which Rheem discontinued on May 2, 2026. Buy its direct replacement, the RTG20235BC (about $18–$26), to fix a Code 11 no-ignition fault. Noritz’s genuine EMUJ004 igniter (about $17–$35) is listed for the N-0751M, N-0931M, NR111 and NRC111 families. Always match the exact part number to your model plate — a wrong-but-similar-looking igniter simply won’t fit or fire correctly.

Last updated October 28, 2026: rechecked every part number against current supplier listings. Rheem discontinued the RTG20235C ignitor coil on May 2, 2026 (per SupplyHouse), and its direct replacement is the RTG20235BC. Distributor fitment lists put the Noritz EMUJ004 on the N-0751M, N-0931M, NR111 and NRC111 families rather than the NR/NRC98 units we listed earlier, and at $16.95–$34.89 it is cheaper than Rinnai’s igniter, not pricier. We also corrected the RL94iN, which is a non-condensing Rinnai.

An igniter failure shows up as one of the most common tankless service calls: the unit tries to fire and fails, throwing a Code 11 (Rinnai, Rheem) or E003 (Navien) fault, as covered in our tankless water heater error codes guide. The part itself is mentioned constantly across troubleshooting content on this site, but which physical igniter you actually need depends entirely on your brand and, in Rinnai’s case, which generation of unit you own. This guide covers the correct genuine replacement for each major brand.

By the numbers

• 0.138 in. (3.5 mm) is the spark electrode gap a Code 11 no-ignition fault gets checked against on Rinnai units, per Rinnai’s own diagnostic manual — too wide or too narrow and a brand-new igniter still won’t reliably arc. — Rinnai troubleshooting documentation
• 11 and 12 are the same fault-code numbers Rinnai and Rheem both use for no-ignition and flame-failure faults, even though the two companies publish entirely separate service manuals — a coincidence covered in more depth in our error codes guide.
• $17–$51 is the price spread across genuine igniters for this guide’s picks in October 2026, from $16.95 for a Noritz EMUJ004 at TanklessParts.com and $17.65 for a Rheem RTG20235BC at SupplyHouse up to $51.02 for a Rinnai 105000230 at HD Supply. Retailer matters more than brand here. — supplier listings, October 2026
• May 2, 2026 is the date SupplyHouse lists for Rheem’s discontinuation of the RTG20235C ignitor coil, naming the RTG20235BC as its direct replacement. Many guides and Amazon listings still show the old number. — SupplyHouse

Igniter compatibility at a glance

1. Rinnai 105000230 Igniter Assembly — Best for Current Rinnai Units

This is the igniter most current Rinnai owners need. It’s the same part used across the condensing RUC98iN, Sensei RX and Infinity platforms and the non-condensing RL94iN and RL92iN — a wide compatibility range for a single SKU, but confirm your exact model against Rinnai’s parts documentation before ordering, since Rinnai has rebranded several of these platforms over the years (the RU199iN-to-Sensei-RX199iN rename we cover in our Rinnai tankless review is a good example of how model names shift while the underlying platform, and its parts, stay the same).

2. Rinnai 105000180 Ignitor — Best for Older Rinnai RL75i/RL94i-VC

If your Rinnai unit’s model plate reads RL75i or RL94i-VC rather than one of the current RUC/RL94iN/Sensei/Infinity names, this — not the 105000230 above — is the correct part. Rinnai has run multiple igniter designs across its product history, which is exactly why matching the part number to your model plate matters more here than in almost any other accessory category on this site.

3. Rheem/Ruud RTG20235BC Ignitor Coil (Replaces RTG20235C) — Best for Rheem, Ruud, and Richmond

Rheem, Ruud, and Richmond tankless heaters share the same underlying manufacturing platform, which is why one igniter part number covers all three badges. If your unit is throwing a Code 11 fault and carries any of these three names on its rating plate, this is the part to check. Older Rheem service manuals and most how-to videos still cite RTG20235C, so search for the BC number or you’ll mostly find leftover or non-OEM stock.

4. Noritz EMUJ004 Igniter — Best for Noritz

At current supplier prices, the Noritz EMUJ004 is one of the cheapest genuine igniters in this guide, about $17–$35 against $39–$51 for Rinnai’s 105000230. The bigger risk with Noritz is fitment, not cost. Noritz has used several igniter part numbers across its model history, so check that EMUJ004 is listed for your exact model before ordering.

The igniter isn’t universal — and that’s the trap

Most of the accessory categories on this site — filters, isolation valve kits, vent kits — have at least some cross-brand or universal options. Igniters don’t work that way. A generic Amazon search for “tankless water heater igniter” returns a mix of furnace pilot igniters, gas-fireplace igniters, and genuinely compatible tankless parts side by side, because the search term isn’t brand-specific enough to filter any of it out. The only reliable way to buy the correct part is to match the exact OEM number — 105000230, 105000180, RTG20235BC, or EMUJ004 — against your unit’s model plate, not just its brand name.

There’s also a DIY tension worth naming honestly: Rinnai’s own troubleshooting manual groups igniter and flame-rod replacement alongside tasks it says require a licensed technician, in the same breath as adjusting the internal gas valve (which genuinely should never be DIY). In practice, igniter replacement is far more accessible than that — it’s an external, unplugged component swap with an abundance of manufacturer parts sold directly to consumers and step-by-step how-to videos for exactly this job. The real safety line is simpler than the manual’s blanket caution suggests: always cut gas and power before starting, and on Rinnai units, re-verify the 0.138 in. spark gap after installing the new igniter — skip that check and a perfectly good new igniter can still throw a repeat Code 11.

How to choose

• Match your brand and exact model first. Check your unit’s rating plate, not just the badge — Richmond, Ruud, and Rheem all use the same ignitor coil (now the RTG20235BC), but Rinnai alone has two non-interchangeable igniter generations.
• Rule out the free fixes before buying a part. A closed gas valve, empty propane tank, or wrong gas-type setting all produce an identical Code 11 fault with no failed hardware at all — see our error codes guide for the full diagnostic order.
• Current Rinnai unit (RUC98iN, Sensei, RL94iN): the 105000230. Older RL75i/RL94i-VC: the 105000180 instead.
• Rheem, Ruud, or Richmond: the RTG20235BC, which replaced the discontinued RTG20235C. One part covers all three badges.
• Noritz: the EMUJ004, after confirming your model is on its fitment list. It’s typically the cheapest of the four.
• After installing on a Rinnai unit, re-verify the 0.138 in. (3.5 mm) electrode gap before closing everything back up.

The bottom line

Unlike most tankless accessories, an igniter is not a part you can buy by search term alone — it has to match your exact brand and, for Rinnai owners, the right generation of unit. Current Rinnai units need the 105000230, older RL75i/RL94i-VC units need the 105000180, Rheem/Ruud/Richmond units share the RTG20235BC (the replacement for the RTG20235C discontinued in May 2026), and listed Noritz models take the EMUJ004. Before buying any of them, work through the free checks in our tankless water heater error codes guide — a closed valve or wrong gas-type setting produces the exact same Code 11 fault as a genuinely failed igniter, and costs nothing to rule out first. And if you’re hoping a simple reset clears the Code 11 before replacing anything, our reset button guide covers the actual (button-free) reset procedure for each brand — it clears the lockout state but won’t fix a genuinely failed igniter. Worth knowing going in: this igniter is doing a job a standing pilot light used to do on older tank heaters — see our pilot light guide for why tankless units replaced that continuous flame with exactly the electronic ignition hardware covered here.