Rheem Water Heater Age Decoder: Find Your Manufacture Date
Last updated: May 2026
Rheem uses an MMYY serial number format: month first, year second. The first two digits are the month of manufacture (01 through 12), and the next two digits are the two-digit year. The decoder below is pre-selected for Rheem and also handles Ruud, Richmond, and Rheem-built GE units, which share the same encoding. If you need help over the phone or want to discuss replacement options, call (641) 637-5215. You can also view the universal decoder for other brands.
Rheem Water Heater Age Decoder
Enter your Rheem serial number. The first four digits encode the month and year of manufacture.
Find the serial number on the rating plate sticker on the side of your water heater, near the warning labels and Energy Guide.
Where do I find my serial number? +
The serial number is printed on the rating plate, a sticker on the side of your water heater near the warning labels and Energy Guide. It is usually in the upper third of the tank, near the gas valve on a gas unit or near the thermostat on an electric unit.
The serial number is typically 8 to 12 characters long and is labeled "Serial No." or "S/N". Do not confuse it with the model number, which is a separate, longer alphanumeric field on the same sticker. If the sticker is faded, use your phone's flashlight and take a photo at an angle to reduce glare.
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How to Read a Rheem Serial Number
Rheem assigns each water heater a serial number printed on the rating plate, a sticker mounted on the side of the tank. The Rheem rating plate uses red and white branding with the Rheem logo at the top. The label lists the model number, serial number, gallon capacity, BTU rating (gas) or kilowatt rating (electric), recovery rate, dip tube material, and the Energy Guide data. On most current production, the plate sits in the upper third of the tank within easy reading height. On gas units, the plate is positioned near the gas valve. On electric units, near the upper thermostat panel.
The serial number field on a Rheem unit contains 12 alphanumeric characters. The first four characters are the date code in MMYY format: month-month-year-year. The remaining eight characters are an internal plant code and a sequence number identifying the specific unit. For age decoding, the first four characters are all you need. The rest is Rheem manufacturing tracking data with no implication for unit age.
The Month (First Two Digits)
The first two digits of a Rheem serial number are the month of manufacture, from 01 (January) through 12 (December). The leading zero is included for single-digit months, so a serial starting with 0322 indicates March 2022, not month 32. If the first two digits exceed 12, the unit is not following the current Rheem MMYY format and may use the older YYWW format used on units made before approximately 2005. The decoder above attempts the modern format first and falls back to the older format if the first two digits exceed 12.
The Year (Third and Fourth Digits)
The third and fourth digits are the last two digits of the year of manufacture. Years 00 through 79 are interpreted as 2000 through 2079, and years 80 through 99 are interpreted as 1980 through 1999. A serial starting with 0398 indicates March 1998. A serial starting with 0320 indicates March 2020. The interpretation rule is the same as on AO Smith units, and for any Rheem still in service the modern interpretation is correct.
Worked Examples
Consider a serial number beginning with 0720. The first two digits (07) indicate July. The next two digits (20) indicate 2020. The unit was manufactured in July 2020 and is approximately 6 years old as of mid-2026. This is within expected lifespan for any Rheem tier (Performance, Plus, Platinum); maintenance rather than replacement is the immediate focus.
Consider a serial number beginning with 1219. The first two digits (12) indicate December. The next two digits (19) indicate 2019. The unit was manufactured in December 2019 and is approximately 6.5 years old. Like the previous example, this is within expected lifespan.
Consider a serial number beginning with 0398. The first two digits (03) indicate March. The next two digits (98) indicate 1998 (because 98 is in the 80-99 range). The unit was manufactured in March 1998 and is approximately 28 years old. This is well past any reasonable expected lifespan, and if it is still in service it should be replaced immediately. A 28-year-old tank water heater is operating on substantially borrowed time.
Consider a serial number beginning with 1305. If you decoded this as month 13 of 2005, the decode would be wrong because there is no month 13. This means either the unit uses the older YYWW encoding (year 13 = 2013, week 05 = late January 2013) or there is a transcription error. The decoder above tries the MMYY format first; if month exceeds 12, it falls back to YYWW and reports the alternate format.
Older Rheem Serial Format (Pre-2005)
Rheem and its sister brands used a different serial format on units produced before approximately 2005. The older format is YYWW (year-week, similar to AO Smith): the first two digits are the year and the next two digits are the week of the year (1 through 52). If your first two digits exceed 12, the unit is likely an older format. The decoder above handles both formats automatically and labels which format was used to produce the result.
Common Mistakes Decoding Rheem Serial Numbers
The first common mistake is reversing month and year. The AO Smith family uses YYWW (year first), and the Rheem family uses MMYY (month first). If you are familiar with AO Smith decoding and apply the same rules to a Rheem, you will get the wrong answer. Rheem month comes first. A Rheem serial starting with 0720 is July 2020, not week 20 of 2007.
The second common mistake is decoding the model number instead of the serial number. Rheem model numbers on residential gas units commonly begin with letters such as PROG (ProLine Performance gas), XG (export gas), or PROGH (high-efficiency gas) followed by capacity codes. The model number is longer than the serial and is labeled "Model" or "Model No." rather than "Serial."
The third common mistake is decoding a non-Rheem GE unit using Rheem rules. GE water heaters were Rheem-made under license between approximately 2009 and 2018. After that, the license arrangement changed. A pre-2018 GE-branded unit will decode correctly using Rheem MMYY rules. A post-2018 GE unit may not. If a GE unit produces an obviously wrong decode, contact GE Appliances with the model and serial for a manual lookup.
Common Rheem Age-Related Issues
Rheem manufactures across a wide tier range, from entry-tier Performance units sold at Home Depot to Marathon non-metallic tanks with multi-decade lifespans. Wear patterns differ by tier. The following describes the typical issue at each age band on residential Rheem tank units.
5 to 7 Years: Gas Valve Sensors and Thermostat Wear
A Rheem Performance, Plus, or Platinum unit in the 5 to 7 year range is generally healthy. On gas Performance units, the most common service issue is gas valve sensor drift. Rheem gas valves on FVIR-compliant Performance models (the residential gas line meeting Flammable Vapor Ignition Resistant standards) use thermistor-based temperature sensing that occasionally drifts and causes the unit to overshoot or undershoot the set temperature. The fix is gas valve replacement, typically $400 to $700 installed.
On electric Performance units, thermostat wear is the most common 5-to-7-year issue. The upper thermostat controls priority heating; failure produces no hot water at all. The lower thermostat controls the larger volume of the tank; failure produces hot water that runs out faster than expected. Thermostat replacement is $200 to $400 installed. On both gas and electric units in this age range, the sacrificial anode rod has typically consumed 30 to 60 percent of its mass.
8 to 10 Years: Sediment, Element Scale, Vent Issues
By 8 to 10 years, sediment accumulation at the tank bottom is common on units that have not been flushed annually. Sediment in this age range can reach a layer two to four inches deep on a 50-gallon tank, reducing effective storage capacity and forcing the heat source to work through the insulating layer. Symptoms include reduced hot water duration, popping or rumbling sounds during firing (gas) or cycling (electric), and longer recovery times.
On electric Performance and Plus units, scale buildup directly on the heating elements is common in hard-water areas. The lower element typically scales first (it sits in the bottom of the tank where sediment accumulates) and can overheat and fail. Element replacement is $200 to $400 installed for a single element.
On gas units in this range, the inducer motor on power-vent models begins to show wear. The inducer motor is a small fan that draws combustion exhaust gases through the vent. A worn inducer becomes louder during operation and may eventually fail to spin up, causing the unit to refuse to fire. Inducer replacement is $300 to $500 installed. Atmospheric-vent gas units do not have inducer motors and bypass this failure mode.
10 to 12 Years: Tank Corrosion, Anode Depletion
At 10 to 12 years, a Rheem Performance entry-tier unit is at end of expected lifespan. Performance Plus units may have one to two more years of expected life because of thicker anode rods. Performance Platinum units are still under tank warranty (12 years) and any tank corrosion failure in this period is a warranty event covered by Rheem.
Discolored hot water that resolves after a few seconds of running indicates internal tank corrosion. The anode rod is typically fully consumed at this age if it has not been replaced. For Performance Platinum owners, file a warranty claim before initiating any repair. The 12-year tank warranty on Platinum is one of the most aggressive in the residential market and should be used when the failure mode qualifies.
12 Years and Beyond: End of Life (Except Marathon)
A Rheem Performance or Plus tank water heater past 12 years is operating beyond its design lifespan. Tank failures at this age are commonly sudden, with the corroded tank shell releasing the full water volume rapidly. Hard-water cities (Phoenix, Las Vegas, Tampa, Orlando) reduce this end-of-life range by 2 to 4 years. See our water heater replacement cost guide for full replacement cost context across brand and tier.
The Marathon line is the exception. Marathon tanks are non-metallic polybutylene-fiberglass composites that do not corrode. A Marathon at 15 or 20 years is still within its expected lifespan and is covered by the limited lifetime tank warranty. The most common Marathon issues at advanced age are heating element wear and electrical control wear, both of which are serviceable without replacing the tank itself.
Rheem Model Lines
Rheem produces residential and commercial water heaters across multiple tiers, with distinct warranty terms, features, and replacement cost ranges. The brand is widely available at Home Depot and through wholesale plumbing supply houses.
Performance (Entry Tier)
Performance is the entry-tier Rheem residential line, sold at Home Depot as the "Rheem Performance" series. Performance includes gas atmospheric-vent (PROG variants), gas power-vent (PROGH variants), and electric (PROE variants). The series carries a 6-year tank and 6-year parts warranty. Lifespan in normal water conditions is 8 to 10 years. Replacement cost in 2026, installed, ranges from $1,000 to $2,400 depending on size and configuration.
Performance Plus (Mid Tier)
Performance Plus adds thicker anode rod construction, improved insulation that produces higher Uniform Energy Factor ratings, and a 9-year tank warranty. Lifespan extends to 10 to 12 years. Replacement cost in 2026 runs $1,200 to $2,700 installed. Performance Plus is positioned as the mid-tier upgrade most plumbers recommend over the entry tier when the cost differential is modest.
Performance Platinum (Top Tier)
Performance Platinum is the top-tier Rheem residential line. The series adds EcoNet Wi-Fi connectivity, a 12-year tank warranty (the longest in the residential conventional tank market), and on some sizes a dual anode rod configuration. Lifespan typically reaches 12 to 14 years. Replacement cost in 2026 runs $1,500 to $3,000 installed. The 12-year warranty alone often justifies the upgrade from Plus to Platinum.
Marathon (Non-Metallic Tank)
Marathon is Rheem's electric-only non-metallic tank water heater line. The tank is a polybutylene-fiberglass composite that cannot corrode in the way that glass-lined steel tanks corrode. Marathon units do not require an anode rod and carry a limited lifetime tank warranty (transferable warranty limited to the original installation location). Marathon units are physically larger and heavier than equivalent steel tanks and cost more upfront. Replacement cost in 2026 runs $2,000 to $3,500 installed. Marathon is a niche choice that pays back through multi-decade lifespan if the home stays under the original owner.
ProTerra (Hybrid Heat Pump)
ProTerra is Rheem's hybrid heat pump water heater line. ProTerra units extract heat from ambient air using a refrigeration cycle and transfer it to the tank, producing 2 to 3 times the efficiency of standard electric tanks. ProTerra qualifies for the federal Energy Efficient Home Improvement Credit (25C) at 30 percent of installed cost up to $600 per year, and for many state and utility rebates. ProTerra carries a 10-year tank warranty. Lifespan typically reaches 12 to 15 years. Replacement cost in 2026 runs $2,200 to $4,500 installed before federal tax credit. See the water heater installation cost guide for ProTerra-specific install considerations.
Tankless (RTGH and RTG Series)
Rheem's tankless gas water heater lineup includes the RTGH condensing series and the non-condensing RTG series. Tankless units do not store hot water, instead heating water on demand as it flows through the unit. Tankless lifespan is 15 to 20 years with annual descaling in hard-water areas, much shorter without. Rheem tankless units carry 12-year heat exchanger and 5-year parts warranties on condensing models. The Rheem tankless serial format follows the MMYY convention. Replacement cost in 2026 runs $2,200 to $4,500 installed depending on flow rate, condensing vs non-condensing, and venting requirements.
Ruud and Richmond Sister Brands
Ruud is Rheem-owned and uses the Ruud branding for the wholesale plumbing supply channel. Ruud water heaters are functionally identical to the equivalent Rheem residential lineup; the differentiation is brand positioning and channel rather than product engineering. Richmond is similarly Rheem-owned and targets retail outlets in some regions. Both brands use the same MMYY serial encoding and have the same warranty patterns at equivalent tiers.
Rheem Repair vs Replacement Decision
The repair-or-replace calculus on a Rheem depends on the tier, the unit's age, and the failure mode. Rheem's 12-year warranty on Performance Platinum is one of the most important factors in this decision because a Platinum unit under warranty can have a free tank replacement on a corrosion failure that would otherwise prompt a full unit replacement.
Repair Costs Common to Rheem
The most common Rheem service items and typical 2026 installed costs: anode rod replacement at $150 to $300, electric heating element replacement at $200 to $400 (single) or $300 to $500 (both), thermostat replacement at $200 to $400, gas valve assembly replacement at $400 to $700, dip tube replacement at $150 to $300, T and P valve replacement at $50 to $150, and inducer motor replacement on power-vent units at $300 to $500. ProTerra heat pump-specific repairs (compressor, fan, refrigerant line) can run $600 to $1,500 depending on the component.
Parts availability for Rheem is good through both Home Depot (consumer-facing) and plumbing supply houses (wholesale). The wide retail availability means common parts are usually same-day in metro areas.
Replacement Costs Common to Rheem
Replacement cost ranges in 2026, installed: Performance 40 to 50 gallon at $1,000 to $2,400; Performance Plus 50 gallon at $1,200 to $2,700; Performance Platinum 50 to 80 gallon at $1,500 to $3,000; Marathon 50 to 105 gallon at $2,000 to $3,500; ProTerra 50 to 80 gallon at $2,200 to $4,500 before federal tax credit; tankless RTGH at $2,200 to $4,500. Add $200 to $500 for emergency replacement, $300 to $800 for venting modification, $200 to $500 for expansion tank if required.
The 50 Percent Rule Applied to Rheem
Apply the 50 percent rule: if repair exceeds 50 percent of replacement cost and the unit is past half of expected lifespan, replace. On a 9-year-old Performance entry-tier (past half of 8 to 10 year life), any repair over $600 to $800 warrants replacement discussion. On a 9-year-old Performance Platinum (still within tank warranty), a tank failure is a warranty event and a non-tank failure should be evaluated using the 50 percent rule against the unit's remaining 3 years of warranty.
Warranty Leverage as a Decision Factor
Rheem's warranty terms can shift the repair-or-replace decision significantly. A tank corrosion failure on a 10-year-old Performance Platinum (still under 12-year tank warranty) costs the homeowner nothing for the tank itself, only labor for installation. The economics favor warranty replacement even when an off-the-shelf upgrade might be tempting. For Performance Plus (9-year warranty) and Performance (6-year), warranty leverage applies only within those windows. Always check warranty status before making the repair-or-replace call.
Frequently Asked Questions
Rheem uses an MMYY serial number format: the first two digits are the month of manufacture (01 through 12), and the next two digits are the two-digit year. A serial number beginning with 0720 was manufactured in July 2020. A serial beginning with 1219 was manufactured in December 2019. Years 80 through 99 are interpreted as 1980 through 1999. Enter your full serial number into the decoder above for the exact date and current age.
The serial number is printed on the rating plate, a sticker mounted on the side of the tank in the upper third. On gas units, the plate is near the gas valve. On electric units, it is near the upper thermostat access panel. The Rheem label uses red and white branding and lists the model number, serial number, capacity, BTU or kilowatt rating, recovery rate, and Energy Guide data. The serial number field is labeled "Serial Number" or "Serial." Look for the 12-character alphanumeric string; the first four characters are the date code.
The first two digits of the serial number are the month, the next two are the year. So a serial starting with 0322 indicates March 2022. A serial starting with 1124 indicates November 2024. The remaining characters are a plant code and a sequence number unique to that batch. Older Rheem units (manufactured before approximately 2005) sometimes use a different YYWW format more similar to AO Smith encoding; the decoder above tries the MMYY format first and falls back to YYWW if MMYY does not produce a valid month value.
Rheem tank water heaters typically last 8 to 12 years in normal water conditions, in line with the industry average. Performance entry-tier units cluster at the lower end (8 to 10 years), while Performance Plus and Performance Platinum units cluster at 10 to 13 years because of thicker anode rods and improved heat-loss insulation. Rheem ProTerra hybrid heat pump units typically last 12 to 15 years. The Rheem Marathon, which has a non-metallic polybutylene tank, has an unusually long expected lifespan and ships with a limited lifetime tank warranty.
Yes for Ruud and Richmond, which are Rheem-owned brands and use the same MMYY encoding. GE water heaters built between approximately 2009 and 2018 were also manufactured by Rheem under license and use the MMYY format. After 2018 the GE water heater license arrangement changed; newer GE units may be made by a different manufacturer and may not follow the Rheem encoding. If you have a GE unit with an unfamiliar serial format and the MMYY decode produces an obviously wrong result, contact GE Appliances with the model and serial number.
Rheem Performance entry-tier units carry a 6-year tank and 6-year parts warranty. Performance Plus units carry 9-year tank warranties. Performance Platinum units carry 12-year tank warranties, the longest in the residential tank lineup. Marathon non-metallic units carry a limited lifetime tank warranty. ProTerra hybrid heat pump units carry a 10-year tank warranty. Calculate the unit's age from the serial number and compare to your specific model. Rheem can confirm warranty status from the serial and model number on file.
Performance is Rheem's entry tier, with a single magnesium anode rod, basic insulation, and a 6-year warranty. Performance Plus adds a thicker anode rod, improved insulation that produces a higher Uniform Energy Factor rating, and a 9-year warranty. Performance Platinum adds Wi-Fi connectivity through the EcoNet smart-control system, dual anode rod configuration on some sizes, the highest insulation rating in the tank lineup, and a 12-year warranty. The price differential between Performance and Performance Platinum at retail typically runs $300 to $700; the warranty differential alone often justifies the upgrade.
The Rheem Marathon is a non-metallic tank water heater. The tank is made from polybutylene reinforced with fiberglass instead of glass-lined steel. Because the tank is not metal, it cannot corrode in the way that conventional water heaters do. Marathon units do not require an anode rod (there is no steel to protect) and the tank itself is warranted for the lifetime of the original purchaser as long as it remains in the original installation location. Marathon units are electric only and are physically heavier and somewhat larger in dimension than equivalent steel tanks. Replacement cost is higher than a standard Performance electric ($2,000 to $3,500 installed in 2026), but the multi-decade tank lifespan can offset the premium.
EcoNet is Rheem's Wi-Fi smart-control system, found on Performance Platinum and ProTerra units. EcoNet connects the water heater to a homeowner's phone via the EcoNet app and provides remote temperature control, energy usage tracking, leak and operational fault alerts, and vacation-mode scheduling. EcoNet can also integrate with utility demand-response programs in participating areas, allowing the utility to briefly defer water heater operation during peak grid demand in exchange for billing credits. EcoNet itself does not affect the water heater's lifespan; it is a monitoring and control overlay on top of the conventional heater hardware.
A 10-year-old Performance entry-tier unit is past warranty and at end of expected lifespan; replacement is the cleaner decision unless the failure is very simple. A 10-year-old Performance Platinum unit is still under tank warranty (12 years), so any tank failure is covered. For non-tank failures (gas valve, thermostat, dip tube), apply the 50 percent rule: if the repair quote exceeds 50 percent of replacement cost, replace. The 12-year warranty on Performance Platinum means a tank corrosion failure at 10 years is a warranty event, not a replacement decision.
Methodology and Independence
Plumbing Price Guide is an independent pricing research resource. Cost ranges on this page are compiled from public manufacturer documentation, plumbing supply house pricing across major metro markets, contractor labor surveys, and homeowner-reported installation invoices. Lifespan ranges are based on aggregate manufacturer-published expected service life adjusted for water-quality and use-pattern factors documented in the plumbing service literature. We do not sell Rheem units, do not receive commissions on referrals to specific contractors, and do not have affiliate relationships with Rheem or its competitors. For a fuller description of how cost research is compiled, see our methodology page.
The decoder logic above uses the Rheem published MMYY format, which has been the standard since approximately 2005. For units made before 2005, the decoder falls back to a YYWW format consistent with Rheem service documentation for that earlier era. If your unit predates 2000 or has an unusual non-standard format, the decoder may not produce a reliable result; contact Rheem directly with the serial and model number for manual lookup.
Get Help With Your Rheem
If you have decoded your Rheem and want to discuss next steps with a licensed plumber, call (641) 637-5215. Have your zip code ready so the call routes to a plumber in your area. The call is free and there is no obligation to schedule service. A plumber can confirm the age decode, inspect the unit if needed, evaluate warranty status, and provide a written estimate for repair or replacement. For brand-agnostic pricing benchmarks before the call, see the water heater installation cost guide and the water heater repair cost guide.
Related Guides
- Universal Water Heater Age Decoder (all brands)
- Bradford White Water Heater Age Decoder
- AO Smith Water Heater Age Decoder
- Water Heater Installation Cost Guide
- Water Heater Repair Cost Guide
- Water Heater Replacement Cost Guide
- Tankless Water Heater Cost Guide
- Pricing Research Methodology
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