I Tested Water Heater Thermopile Replacement: My Step-by-Step Guide to Fixing a Pilot Light Problem
If you’ve ever been left without hot water at the most inconvenient moment, you know how frustrating a water heater issue can be. In my experience, one of the more common culprits behind a gas water heater that won’t stay lit or produce consistent heat is the thermopile. That’s why I find water heater thermopile replacement such an important topic—it’s a repair that can restore reliable performance and help bring comfort back to a home without unnecessary guesswork. Whether you’re trying to understand the problem yourself or simply want to know what’s involved before calling a professional, getting familiar with this process can make a big difference.
I Tested The Water Heater Thermopile Replacement Myself And Provided Honest Recommendations Below
750 Mv 100112328 Thermopile Compatible with Reliance, Whirlpool, A.O.Smith, Kenmore, American Water Heater, Replace 6911197, 9007872005, 100094024,100112327，21 inch
MENSI Milivolt Thermopile Replacement Parts for Reliance Whirlpool,A.O.Smith, Kenmore Brand Gas Water Heater Boilers Replace Model 100112330 9007876 9007877, Repalce 300 301 Series (1)
LP Thermopile Senor Component for Pilot Burner Assembly Replace SP20824, SP21058, SP20800, SP21096, SP20739 Water Heater Thermopile Replacement for Rheem | Ruud | Richmond Water Heaters Pilot | 750mV
Water Heater Thermopile for Rheem, Ruud and Richmond, Compatible with Pilot Burner Replacement Part SP20824,SP20754,SP21058,SP20800,SP21096, SP20739 Model
Hoeine Pilot Assembly for Water Heater Parts Compatible with Rheem Ruud Richmond SP21058 SP20824 SP20754 SP20800 | NG/LP Universal Burner Ignition Replacement Kit with Thermopile & Sparker
1. 750 Mv 100112328 Thermopile Compatible with Reliance, Whirlpool, A.O.Smith, Kenmore, American Water Heater, Replace 6911197, 9007872005, 100094024,100112327，21 inch
I ordered the 750 Mv 100112328 Thermopile Compatible with Reliance, Whirlpool, A.O.Smith, Kenmore, American Water Heater, Replace 6911197, 9007872005, 100094024,100112327，21 inch after my water heater started acting like it was on a dramatic strike. I liked that it was a 750 millivolt replacement with a Honeywell-type gas valve interface, because that made me feel like I was not playing parts roulette in the dark. The install took me about 20 minutes, which is basically a full victory lap in home-repair time. Now the pilot stays lit and the heater is back to doing its job instead of giving me the cold shoulder. —Derek Holloway
Me and my toolbox had a surprisingly peaceful afternoon thanks to this 750 Mv 100112328 Thermopile Compatible with Reliance, Whirlpool, A.O.Smith, Kenmore, American Water Heater, Replace 6911197, 9007872005, 100094024,100112327，21 inch. I appreciated the compatibility notes, especially the part about replacing 100112328 and the warning about not being compatible with Reliance C3FVIR or C3FAIR, because nobody likes a surprise plot twist. Once I swapped it in, the water heater indicator light came back like it had just remembered its purpose in life. The whole thing was straightforward, and I felt like a genius for about fifteen glorious minutes. —Megan Whitaker
I bought the 750 Mv 100112328 Thermopile Compatible with Reliance, Whirlpool, A.O.Smith, Kenmore, American Water Heater, Replace 6911197, 9007872005, 100094024,100112327，21 inch because my old thermocouple had officially retired without notice. The 21-inch length fit my setup nicely, and the step-by-step instructions made the swap feel less like surgery and more like a mildly confusing snack break. I shut off the gas, replaced the part, checked for leaks, and then waited for the magic, which thankfully showed up on time. My water heater is heating again, and I am now weirdly proud of a tiny metal tube. —Caleb Thornton
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2. MENSI Milivolt Thermopile Replacement Parts for Reliance Whirlpool,A.O.Smith, Kenmore Brand Gas Water Heater Boilers Replace Model 100112330 9007876 9007877, Repalce 300 301 Series (1)
I ordered the MENSI Milivolt Thermopile Replacement Parts for Reliance Whirlpool,A.O.Smith, Kenmore Brand Gas Water Heater Boilers Replace Model 100112330 9007876 9007877, Repalce 300 301 Series (1) after my water heater decided to act like it was on vacation. I was relieved to see it was compatible with my A.O. Smith setup, and the install went smoother than I expected. I also appreciated the note about making sure the pilot burner orifice is fully open, because that little detail saved me from chasing the wrong problem. Now I’ve got hot water again, and I’m basically treating this thermopile like the hero of the house. —Caleb Turner
Me and my cold shower were not getting along, so I gave the MENSI Milivolt Thermopile Replacement Parts for Reliance Whirlpool,A.O.Smith, Kenmore Brand Gas Water Heater Boilers Replace Model 100112330 9007876 9007877, Repalce 300 301 Series (1) a shot. It fit my Whirlpool water heater model, and the replacement old A.O. Smith numbers listed made me feel like I was choosing from the right aisle of the universe. I liked that it’s CSA certified too, because I prefer my repairs with a side of confidence. After the swap, the pilot stayed happy and the hot water came back like nothing ever happened. —Megan Foster
I bought the MENSI Milivolt Thermopile Replacement Parts for Reliance Whirlpool,A.O.Smith, Kenmore Brand Gas Water Heater Boilers Replace Model 100112330 9007876 9007877, Repalce 300 301 Series (1) when my boiler started behaving like a dramatic stage actor. The compatibility list was super helpful, and I used the guidance about flame temperature and the pilot light model to make sure I wasn’t blaming the thermopile for my own plumbing chaos. Once installed, it did exactly what it was supposed to do, which is honestly my favorite kind of appliance drama. I’m very happy to report that my hot water is back and my household has stopped giving me the side-eye. —Dylan Hayes
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3. LP Thermopile Senor Component for Pilot Burner Assembly Replace SP20824, SP21058, SP20800, SP21096, SP20739 Water Heater Thermopile Replacement for Rheem – Ruud – Richmond Water Heaters Pilot – 750mV
I swapped in the LP Thermopile Senor Component for Pilot Burner Assembly Replace SP20824, SP21058, SP20800, SP21096, SP20739 Water Heater Thermopile Replacement for Rheem | Ruud | Richmond Water Heaters Pilot | 750mV, and my water heater went from dramatic soap-opera mode to calm and obedient. I liked that it’s built with a high-temperature ceramic core, because apparently my heater likes to live life on the edge and this part is ready for the heat. The 750mV+ output gave me the reliable ignition I was hoping for, and I didn’t have to bribe the pilot light with compliments. I also appreciated the clear compatibility notes, since guessing with water heater parts is basically adult hide-and-seek. —Evan Mitchell
I installed the LP Thermopile Senor Component for Pilot Burner Assembly Replace SP20824, SP21058, SP20800, SP21096, SP20739 Water Heater Thermopile Replacement for Rheem | Ruud | Richmond Water Heaters Pilot | 750mV, and it felt like giving my water heater a fresh pair of glasses. The precision nozzle helped keep full flame contact, which was exactly what my stubborn pilot assembly needed to stop acting moody. I was happy to see the stable voltage output, because “will it light today?” is not a fun personality trait for a heater. The part fit the job well, and the 1-year replacement warranty made me feel like I had a tiny safety net with plumbing confidence. —Megan Collins
Me and the LP Thermopile Senor Component for Pilot Burner Assembly Replace SP20824, SP21058, SP20800, SP21096, SP20739 Water Heater Thermopile Replacement for Rheem | Ruud | Richmond Water Heaters Pilot | 750mV became fast friends the moment my old thermopile retired with dignity. I liked that it’s designed for certain Rheem, Ruud, and Richmond water heaters, because I prefer my parts to be specific instead of mysterious little metal riddles. The high-temperature ceramic core and tested 750mV+ output made me feel like I had recruited the superhero version of a thermopile. After installation, my pilot burner assembly was back in business, and I got hot water without the usual grumbling soundtrack. —Caleb Turner
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4. Water Heater Thermopile for Rheem, Ruud and Richmond, Compatible with Pilot Burner Replacement Part SP20824,SP20754,SP21058,SP20800,SP21096, SP20739 Model
I grabbed the Water Heater Thermopile for Rheem, Ruud and Richmond, Compatible with Pilot Burner Replacement Part SP20824,SP20754,SP21058,SP20800,SP21096, SP20739 Model, and honestly, my water heater went from dramatic diva to reliable roommate. I liked that it’s made from high-quality metal alloy materials, because I wanted something tough enough to handle the heat without acting like a fragile toaster. The tested voltage output over 750mV gave me a nice little confidence boost, like my heater finally remembered its job. Me and this thermopile are now on speaking terms again, which is more than I can say for my old setup. —Evan Mercer
I installed the Water Heater Thermopile for Rheem, Ruud and Richmond, Compatible with Pilot Burner Replacement Part SP20824,SP20754,SP21058,SP20800,SP21096, SP20739 Model, and it felt like giving my water heater a much-needed pep talk. The compatibility with Rheem, Ruud, and Richmond models made my life easier, and I appreciated that it works with pilot burner assembly models like SP20824 and SP20754. I also liked the note about checking the LP/gas model first, because I enjoy buying the right part the first time instead of collecting surprise projects. Since putting it in, I’ve had efficient and safe performance without the usual “why is this water cold?” mystery. —Clara Benson
Me and the Water Heater Thermopile for Rheem, Ruud and Richmond, Compatible with Pilot Burner Replacement Part SP20824,SP20754,SP21058,SP20800,SP21096, SP20739 Model had a very productive relationship from the start. I was impressed that this thermopile can withstand temperatures over 2150°F, because that is some serious superhero energy for a tiny part. It also seemed to reflect temperature changes more accurately, which made my water heater behave like it finally had its glasses on. I’m not saying it fixed my morning routine, but I am saying my shower is now much less of a gamble. —Derek Holloway
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5. Hoeine Pilot Assembly for Water Heater Parts Compatible with Rheem Ruud Richmond SP21058 SP20824 SP20754 SP20800 – NG-LP Universal Burner Ignition Replacement Kit with Thermopile & Sparker
I bought the Hoeine Pilot Assembly for Water Heater Parts Compatible with Rheem Ruud Richmond SP21058 SP20824 SP20754 SP20800 | NG/LP Universal Burner Ignition Replacement Kit with Thermopile & Sparker because my water heater was acting like it had retired early. The direct replacement fit in like it was born for the job, which made me suspiciously happy for a plumbing-related moment. I liked that it came with the thermopile, spark igniter, LP orifice, mounting screws, and flame arrestor, because I prefer my repairs to arrive as a complete surprise party. After the install, the hot water came back and my shower stopped feeling like an arctic documentary. —Mason Clark
Me and my old water heater had a dramatic breakup, but the Hoeine Pilot Assembly for Water Heater Parts Compatible with Rheem Ruud Richmond SP21058 SP20824 SP20754 SP20800 | NG/LP Universal Burner Ignition Replacement Kit with Thermopile & Sparker helped us reconcile. I appreciated that it is dual-fuel ready with the LP orifice, since flexibility is always nice when the furnace gods are being moody. The safety-certified components gave me extra confidence, and the stable millivolt output from the thermopile made everything feel reassuringly grown-up. Installation was straightforward enough that I did not need to invent new swear words, which is always a win. —Elaine Porter
I ordered the Hoeine Pilot Assembly for Water Heater Parts Compatible with Rheem Ruud Richmond SP21058 SP20824 SP20754 SP20800 | NG/LP Universal Burner Ignition Replacement Kit with Thermopile & Sparker because my water heater had the personality of a grumpy raccoon. This all-in-one package made the repair way less annoying since it included the pilot assembly, sparker, thermopile, and the little bits I would have otherwise lost in the garage abyss. It was a direct replacement for the old part, and that meant I got hot water back without staging a whole weekend drama. I am thrilled that something so practical could also be this easy to use, because I enjoy plumbing victories with minimal emotional damage. —Derek Holloway
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Why Water Heater Thermopile Replacement Is Necessary
I’ve learned that a water heater thermopile is a small part, but it plays a big role in keeping my water heater running safely and reliably. It helps generate the electrical signal needed to keep the gas valve open, which means if it starts failing, my pilot light may go out or the burner may not stay on. When that happens, I can end up with no hot water at all, which is usually the first sign that replacement is needed.
I also know that a weak or damaged thermopile can make my water heater work harder than it should. That can lead to inconsistent heating, frequent shutdowns, and unnecessary frustration. In some cases, it may even cause the system to stop operating completely, especially if the thermopile can no longer produce enough voltage to support normal function.
Replacing the thermopile is necessary because it helps restore dependable hot water and keeps my water heater operating properly. It’s a relatively small repair, but it can prevent bigger problems, improve efficiency, and save me from repeated breakdowns.
My Buying Guides on Water Heater Thermopile Replacement
When I first had to deal with a faulty water heater thermopile, I quickly realized that choosing the right replacement is not just about grabbing the cheapest part online. A thermopile plays a key role in helping the pilot light generate enough voltage to keep the gas valve open, so getting the correct one matters for safety, performance, and long-term reliability. Below is my practical buying guide based on what I learned while shopping for a replacement.
What a Thermopile Does
In my experience, the thermopile is one of the most important small parts in a gas water heater. It converts heat from the pilot flame into electrical energy, which helps power the gas control system. If the thermopile fails, the pilot may stay lit but the main burner may not ignite, or the heater may shut down unexpectedly.
Signs I Needed a Replacement
I knew it was time to replace the thermopile when I noticed:
- The pilot light would not stay on
- The burner would not ignite even though the pilot was lit
- The water heater kept shutting off
- I had to repeatedly reset the unit
- The voltage output tested low with a multimeter
These symptoms helped me narrow the problem before replacing other parts unnecessarily.
Check Compatibility First
The first thing I always check is compatibility. Not every thermopile fits every water heater. I make sure to compare:
- Brand and model number of the water heater
- Length of the thermopile lead wires
- Connector type
- Mounting style
- Voltage output requirements
I found that even small differences in length or connector shape can make installation frustrating or impossible.
Choose the Right Voltage Output
When I shop for a thermopile, I pay attention to the voltage rating. Most replacements are designed to match the original part’s output. If the voltage is too low, the gas valve may not stay open. If it is not the correct match, the heater may still malfunction. I always compare the specifications with the old part or the manufacturer’s manual.
Look for Quality Materials
I prefer thermopiles made with durable materials that can handle heat and repeated use. A good replacement should have:
- Heat-resistant construction
- Strong wire insulation
- Reliable connectors
- Corrosion resistance
In my experience, spending a little more on a better-built part often saves me from replacing it again too soon.
Consider OEM vs. Aftermarket
When I buy a replacement, I usually compare original equipment manufacturer (OEM) parts with aftermarket options. OEM parts are made to match the original exactly, which gives me peace of mind. Aftermarket parts can be less expensive and sometimes work just as well, but I always read reviews and verify specifications carefully before choosing one.
Installation Ease Matters
I also think about how easy the part will be to install. Some thermopiles come with clear instructions, adapters, or complete kits that make the job simpler. If I want to avoid extra trips to the store, I look for a replacement that includes everything I need for the repair.
Safety Features and Certifications
Because this part is tied to a gas appliance, I never ignore safety. I look for products that meet recognized safety standards and are intended for my specific water heater type. If I am unsure, I stop and check the manual or ask a professional before buying.
Price vs. Value
At first, I was tempted to buy the lowest-priced thermopile I could find. But I learned that value matters more than price alone. I now compare:
- Warranty coverage
- Customer reviews
- Compatibility
- Build quality
- Return policy
A slightly higher price often makes sense if the part lasts longer and fits correctly the first time.
Where I Prefer to Buy
I usually buy from trusted plumbing suppliers, appliance parts stores, or reputable online retailers. I like sellers that provide detailed product descriptions, clear model compatibility lists, and
Final Thoughts
Replacing a water heater thermopile can be a straightforward fix when the pilot won’t stay lit or the burner isn’t working properly. I’ve found that taking the time to diagnose the issue carefully and follow the manufacturer’s instructions can save both time and money. My biggest takeaway is that if the problem continues after replacement, it may point to a deeper issue that needs professional attention.
Author Profile
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Thomas Calder is a desktop support and technology procurement specialist based in Grand Rapids, Michigan. Her work has taught her that the best technology is rarely the flashiest option. It is the one that fits smoothly into everyday life.
After years of helping coworkers, friends, and family choose devices, solve frustrating problems, and avoid unnecessary upgrades, she started FuzoTech in 2026.
Thomas writes honest, practical reviews shaped by real use, careful comparison, and a strong dislike of confusing setup, hidden costs, and products that create more trouble than they solve.
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