Water Heater Age Decoder: Find Your Manufacture Date

Last updated: March 2026

By the Plumbing Price Guide Team

Most homeowners have no idea how old their water heater is until the day it fails. The manufacture date is encoded directly in the serial number on the rating plate sticker, but every manufacturer uses a different format. This decoder handles all major brands in the browser instantly, with no account or signup required.

Why Your Water Heater's Age Matters

Most homeowners do not know how old their water heater is until the day it fails. This is a significant financial blind spot. A standard tank water heater that fails unexpectedly can release 40 to 80 gallons of water in minutes, causing $5,000 to $15,000 in water damage to floors, walls, and personal property. Emergency water heater replacement costs $200 to $500 more than a planned replacement because of rush scheduling, after-hours labor rates, and limited unit selection.

The average tank water heater lasts 8 to 12 years. Tankless units last 15 to 20 years. Knowing your unit's age gives you a replacement planning window instead of a crisis. A homeowner who knows their water heater is 9 years old can budget for replacement over the next year or two, shop on their schedule, compare unit types and efficiency options, and time the replacement during a plumber's normal business hours. See our plumbing emergency guide for what to do if your water heater fails before you can plan for replacement.

The manufacture date encoded in the serial number is the date the unit was built, which may be several months before it was installed in your home. Both dates matter, but the manufacture date is the more conservative estimate of age and the one used to assess remaining lifespan.

How to Find Your Water Heater Serial Number

The serial number is printed on the rating plate, a sticker affixed to the side of the water heater. On most units, the rating plate is in the upper third of the tank, near the gas valve on gas water heaters or near the thermostat controls on electric units. The sticker also shows the model number, BTU rating or kilowatt rating, energy efficiency data, and installation warnings.

Serial Number vs Model Number: Know the Difference

These two fields appear on the same rating plate sticker and are frequently confused. The model number identifies the product design and specifications, typically a combination of letters and numbers that describes the type, size, and features of the unit. The serial number is unique to each individual unit and encodes the manufacture date. The serial number field on the sticker is labeled "Serial No." or "S/N." Model numbers are usually longer and contain size codes.

Tips for Reading a Faded Sticker

Water heater rating plate stickers age, particularly in humid utility rooms, garages, and basement environments. If the sticker is difficult to read, try these approaches in order:

• Use your phone's flashlight and hold it at a low angle to the sticker surface; the raking light highlights characters that are hard to see straight-on.
• Photograph the entire sticker and zoom in on the photo; the camera sometimes captures detail that the eye misses in poor lighting.
• Try a photo with flash and another without; compare both for readability.
• If the sticker is illegible, check whether the same information appears on a service record sticker attached by a plumber during a previous service visit.
• Contact the manufacturer with the model number and any partial serial number; most manufacturers can look up manufacture date from a partial serial number or model number.

Photograph the Entire Rating Plate

Once you have the serial number, take a clear photo of the entire rating plate and save it in a home maintenance file, home inspection folder, or email it to yourself. You will want this information if you ever need to contact the manufacturer about a warranty issue, file an insurance claim, or disclose the water heater condition during a home sale.

How Each Brand Encodes the Manufacture Date

Every water heater manufacturer uses a different system to encode the manufacture date in the serial number. Understanding the system for your brand is the key to decoding the date. The tool above handles all of this automatically, but the following explains each system in detail for homeowners who want to verify the result or decode manually.

AO Smith, State, Reliance, Whirlpool, American Water Heater

AO Smith is one of the largest water heater manufacturers in the U.S. and produces units sold under the AO Smith, State, Reliance, American Water Heater, US Craftmaster, and Whirlpool brand names. All of these brands use the same serial number format: the first two characters are the two-digit year of manufacture, and the next two characters are the week of manufacture (1 through 52 or 53).

A serial number beginning with "2037" was manufactured in week 37 of 2020, which falls in mid-September 2020. A serial number beginning with "1852" was manufactured in week 52 of 2018, approximately late December 2018. For units manufactured before 2000, the two-digit year 80 through 99 corresponds to 1980 through 1999.

Rheem, Ruud, Richmond, GE

Rheem manufactures water heaters sold under the Rheem, Ruud, Richmond, and General Electric (GE) brand names. The Rheem serial number format is month-year (MMYY): the first two digits are the month (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 number beginning with "1219" was manufactured in December 2019. Some older Rheem models used a different format; the tool handles this automatically.

Bradford White

Bradford White uses an alphabetic code rather than a numeric code. The first letter of the serial number represents the year of manufacture, and the second letter represents the month of manufacture. The letters I and O are skipped in both the year and month code sequences to avoid confusion with the numbers 1 and 0.

The year codes cycle every 20 years: A represents 1984, 2004, and 2024; J represents 1992 and 2012; S represents 2000 and 2020; and so on through V, which represents 2003 and 2023, at which point the cycle returns to A for 2024. Because the codes cycle, a Bradford White serial number can correspond to two possible years 20 years apart. The tool defaults to the most recent possible year and notes the earlier alternative.

The month codes run A through M (skipping I), where A is January and M is December. A Bradford White serial number beginning with "JH" was manufactured in August 2012 (J = 2012, H = August). A serial beginning with "SB" was manufactured in February 2020 (S = 2020, B = February).

Rinnai

Rinnai changed its serial number format in 2009. Units manufactured before 2009 use a numeric format where the first two digits are the year and the third and fourth digits are the month. A serial number beginning with "0403" was manufactured in March 2004.

Units manufactured in 2009 and later use an alphabetic format similar to Bradford White, where the first letter encodes the year and the second letter encodes the month. For Rinnai, A = 2009, B = 2010, and so on through the alphabet (skipping I and O). The month codes are the same as Bradford White: A = January through M = December, skipping I. A serial containing "CA" as the first two alpha characters was manufactured in January 2011 (C = 2011, A = January).

Navien

Navien tankless water heaters encode the manufacture date in the first six digits of the serial number: year (2 digits), month (2 digits), and day (2 digits). A serial number beginning with "210315" was manufactured on March 15, 2021. Navien's precision makes their serial numbers among the most informative of any manufacturer.

Noritz

Noritz tankless water heaters commonly use a four-digit format at the start of the serial number: two digits for the year and two digits for the month. A serial number beginning with "1806" was manufactured in June 2018.

Bosch

Bosch water heater serial numbers typically begin with the letters "FD" followed by a four-digit code where the first two digits are the year and the last two digits are the month. A serial number beginning with "FD2106" was manufactured in June 2021.

Kenmore

Kenmore water heaters are manufactured by different companies depending on the model. To determine which decoding system to use, check the first three digits of the model number (not the serial number) on the rating plate. If the model number begins with "153," the unit was manufactured by Rheem and uses the Rheem MMYY decoding format. Most other Kenmore model number prefixes indicate AO Smith manufacture, which uses the YYWW format.

What Your Water Heater's Age Means

The age of a tank water heater is the single most important factor in assessing its replacement priority, more so than any other factor except an active failure symptom. Here is how to interpret your unit's age in practical terms.

0 to 5 Years: Prime Working Life

A water heater in its first five years is performing within its design parameters. Focus on basic maintenance rather than replacement planning. Flush the tank annually to remove sediment before it accumulates. Have the anode rod inspected at year three or four, particularly in hard water areas. Test the temperature and pressure relief valve annually by briefly lifting the lever and verifying water flows into the discharge pipe.

5 to 8 Years: Healthy Midlife

Your water heater is still within its expected lifespan but has used a significant portion of it. Start paying attention to performance changes: does the hot water run out faster than it used to? Are you hearing any new sounds from the tank? Have the anode rod replaced if it has not been done yet. Begin budgeting for eventual replacement in general home maintenance planning. This is also a good time to research whether your next unit will be a tank or tankless and what rebates or tax credits are available in your area.

8 to 10 Years: Approaching End of Average Lifespan

At 8 to 10 years, a tank water heater has reached or is approaching the end of the average U.S. lifespan. If you are in a hard water city such as Las Vegas, Phoenix, Orlando, or Tampa, where water quality shortens heater life by 2 to 4 years, you are at or past the end of the adjusted lifespan. Have a plumber inspect the unit. If the anode rod is fully depleted and the tank shows internal corrosion signs, replacement is the wiser investment. For guidance on replacement options in specific cities, see our guides for Chicago and Louisville.

10 to 12 Years: Past Average Lifespan

A tank water heater at 10 to 12 years is past the average lifespan. Replacement should be a near-term priority. The risk of failure increases substantially each year in this range. If you notice any warning signs, such as rusty water, sediment sounds, or a visible leak, move replacement to the front of the priority list. If the unit is in a location where a failure would cause significant damage (above finished living space, in a closet adjacent to bedrooms, near electronics), do not wait for a warning sign.

12 or More Years: On Borrowed Time

A tank water heater at 12 or more years has exceeded its design lifespan. Tank corrosion at this age is significant, and the failure mode is often sudden and complete: the tank bottom or side corrodes through and releases its full water volume rapidly. The cost difference between a planned replacement and an emergency replacement ($200 to $500) is negligible compared to the $5,000 to $15,000 in water damage a tank failure can cause. Replace this unit as soon as possible.

Note: Tankless water heaters have a lifespan of 15 to 20 years, and the above timelines apply specifically to tank units. Hard water areas such as Las Vegas shorten tank lifespan by 2 to 4 years from the above benchmarks.

Signs Your Water Heater Is Failing (Regardless of Age)

Age provides the statistical probability of failure, but certain symptoms indicate active failure or imminent failure regardless of the unit's age. If you observe any of the following, contact a plumber and see our water heater repair cost guide to understand your options.

Rusty or Discolored Hot Water

Rust-colored or brown water from the hot water taps indicates that the anode rod has been fully consumed and the tank is corroding from the inside. Anode rod replacement at $150 to $300 may be appropriate if the unit is relatively young (under 7 years) and the corrosion is minimal. On an older unit, internal corrosion that has progressed to discolored water output means the tank will fail in the near future; replacement is the appropriate response.

Rumbling, Popping, or Banging Noises

Loud noises from the water heater, particularly when it is heating, are caused by water boiling beneath a layer of sediment on the heating element or at the tank bottom. The sediment layer insulates the element, causing overheating and steam bubble formation. This condition reduces efficiency, accelerates element and tank wear, and if ignored, will cause element failure. Annual tank flushing prevents sediment accumulation. If your tank is already making significant noises, have it inspected; the element may already be damaged.

Water Pooling Around the Base

Any water visible around the base of a water heater requires immediate investigation. Condensation can form on the exterior in humid environments, which is normal. Water pooling consistently at the base, especially after the condensation explanation has been ruled out, indicates a leak from the tank body, a fitting, the drain valve, or the T&P relief valve discharge. A leak from the tank body itself means replacement is necessary; there is no repair for a corroded-through tank shell.

Hot Water Runs Out Faster Than Before

If your 50-gallon tank water heater is delivering 20 minutes of hot water when it previously delivered 40 minutes, sediment has accumulated at the bottom and is displacing water volume. The effective storage capacity has been reduced. Annual flushing restores this capacity if caught early. Advanced sediment accumulation may also indicate a failed bottom heating element in electric units.

Inconsistent Water Temperature

Temperature swings during a shower or at the tap may indicate thermostat failure, a failing heating element (electric), or a gas valve issue (gas). These are generally repairable components, but the repair cost on an older unit should be weighed against replacement using the 50 percent rule described in the FAQ below.

Visible Rust or Corrosion on the Exterior

External rust or corrosion on the tank jacket (the outer shell) suggests the unit has been in a humid or wet environment. External corrosion can accelerate internal corrosion and indicates the unit's physical integrity is compromised. If the rust is on the connections, fittings, or at the top of the tank where the pipes enter, the corrosion may be addressable without replacement. If the rust covers significant portions of the tank body, the unit should be replaced.

Location Risk: Consider the Damage Potential

A water heater installed in a finished basement, an upstairs utility closet above living space, or in a location adjacent to electronics, furniture, or irreplaceable items represents a higher damage risk than one in an unfinished basement or a garage. If your unit is in a high-damage-potential location and is 8 years or older, the risk calculus favors proactive replacement even without a specific failure symptom. See our guide on when to call a plumber for more on evaluating urgency.

Water Heater Replacement Costs in 2026

Understanding replacement costs before you need to replace your water heater allows you to budget accurately and evaluate contractor quotes fairly. The following are installed costs including the unit, all necessary fittings, labor, and local permit fees where required.

Federal Tax Credits for Heat Pump Water Heaters

The federal Energy Efficient Home Improvement Credit (25C) provides a tax credit of 30 percent of the installed cost of qualifying heat pump water heaters, up to $600 per year. This credit applies to heat pump (hybrid) electric water heaters that meet the ENERGY STAR criteria. A heat pump water heater installed for $3,500 would generate a $600 federal tax credit, reducing the net cost to $2,900. Combine this with utility rebates available from many local utilities and the long-term energy savings to get the full financial picture. See our water heater installation cost guide for detailed cost breakdowns by brand, size, and region.

Emergency vs Planned Replacement Premium

When a water heater fails suddenly, the homeowner faces emergency pricing: after-hours labor rates, rush delivery of units from a distributor or big-box store (limiting selection), and the time pressure of a flooded utility room or no hot water. This premium typically runs $200 to $500 above the cost of a planned replacement. Over the long run, homeowners who know their water heater age and plan replacements proactively spend significantly less than those who wait for failure.

For labor rate context when evaluating quotes, see our plumber cost per hour guide. For a personalized cost estimate based on your region and situation, use our plumbing cost calculator.

How to Extend Your Water Heater's Lifespan

Several maintenance practices can add years to a water heater's service life and reduce the likelihood of a sudden failure. In hard water areas, these practices are particularly important because water quality accelerates the natural wear mechanisms.

Annual Tank Flushing

Flush the tank once a year under normal conditions; every six months in hard water areas such as Phoenix, Las Vegas, Tampa, and Orlando. Flushing removes accumulated sediment from the tank bottom before it insulates the heating element or creates a corrosion-promoting environment. A plumber can flush the tank during an annual service visit ($100 to $200), or a mechanically capable homeowner can do it by connecting a garden hose to the drain valve on the tank and draining until the water runs clear.

Anode Rod Inspection and Replacement

The sacrificial anode rod is a rod of magnesium, aluminum, or aluminum-zinc-tin alloy suspended inside the tank. It corrodes preferentially over the steel tank shell, protecting the tank from internal corrosion through an electrochemical process. Once the anode rod is consumed, the tank shell begins to corrode directly. Inspect the anode rod every three to five years; replace it when more than 50 percent is consumed. In hard water areas, anode rod consumption is faster; inspect every two to three years. Anode rod replacement is a $20 to $50 part that costs $150 to $300 if a plumber does the work. This single investment can extend tank life by several years.

Thermostat Setting

The EPA recommends setting the water heater thermostat to 120 degrees Fahrenheit for most households. Temperatures above 120 degrees accelerate sediment formation because calcium and magnesium carbonate precipitate faster at higher temperatures. They also accelerate anode rod consumption and increase energy cost. The 120-degree setting provides water hot enough to prevent Legionella growth while minimizing thermal wear on the tank.

Water Softener Installation

In hard water areas, a whole-house water softener is the single most impactful investment for extending water heater life. Soft water does not deposit calcium and magnesium carbonate scale on the heating element or at the tank bottom. In cities with very hard water such as Las Vegas and Phoenix, a softener can extend tank water heater life from 6 to 8 years to the national average of 10 to 12 years, representing two to four years of additional service life worth roughly $400 to $800 per year in amortized replacement cost. A water softener costs $1,200 to $3,500 installed.

Expansion Tank Installation

Many modern homes have a backflow preventer on the water meter or at the pressure reducing valve, creating a closed plumbing system. In a closed system, thermal expansion of water in the water heater has nowhere to go and creates pressure spikes each time the unit heats a cycle. Over time, this pressure cycling stresses the tank, the T&P valve, and the fittings. An expansion tank ($100 to $300 for the tank, $150 to $400 labor) provides a chamber for the expanding water volume and eliminates the pressure cycling stress. Many building codes now require expansion tanks in all new water heater installations.

T&P Valve Annual Test

The temperature and pressure relief valve is the safety device that prevents the tank from rupturing if temperature or pressure exceeds safe limits. Test it annually by briefly lifting the lever until water discharges from the discharge pipe, then releasing it. The valve should snap back and stop flowing. A valve that continues to dribble after testing is stuck open and should be replaced immediately ($50 to $150). A valve that is corroded shut provides no safety protection and should also be replaced.

Keep the Area Around the Water Heater Clear

Gas water heaters require combustion air; items stored against the unit can restrict airflow and affect combustion efficiency. All water heaters benefit from accessible clearance around all sides to allow for inspection, maintenance, and rapid response if a leak occurs. Many building codes require a minimum 18-inch clearance in front of the unit for service access. Keep flammable materials well away from gas water heaters.

Frequently Asked Questions

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• Plumbing Emergency Guide
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