# Water Heater Anode Rod by Model: Which Thread, Which Length and Which of the Three Rod Types Fits Your Tank > Residential anode rods are 3/4 inch NPT with a 1-1/16 inch hex head. Rheem publishes 42, 44, 54 and 58 inch rods; Bradford White cuts segmented rods to length. | | | |---|---| | Source | https://ownerspec.com/plumbing/parts/water-heater-anode-rod-by-model/ | | Publisher | OwnerSpec (https://ownerspec.com/) | | Published | 2026-09-21 | | Updated | 2026-09-21 | | Facts verified | 2026-09-21 | | Disclosure | Contains affiliate links. OwnerSpec may earn a commission at no cost to the reader. | --- ## Short answer A residential water heater anode rod threads into a 3/4 inch NPT port on almost every US tank. Bradford White's January 2025 service bulletin states its segmented anode connections are 3/4 inch NPT and are intended for any model with a 3/4 inch NPT, and Corro-Protec publishes 3/4 inch NPT for every residential model but its 1 inch Buderus version. Length is the spec makers rarely print: Rheem's parts catalog lists 42, 44, 54 and 58 inch rods, while Bradford White expects a segmented rod to be cut to length in the field. Three materials exist. Magnesium is the default. Aluminium or aluminium zinc is the usual swap when the hot water smells of rotten eggs, which A.O. Smith's manual describes as replacing the anode with one of less active material and then chlorinating. A powered anode replaces the sacrificial rod entirely. The hex head is 1-1/16 inch on all of them. ## Fact sheet - **Answer:** Almost every US residential water heater anode rod threads into a 3/4 inch NPT port and comes out with a 1-1/16 inch hex socket, per Bradford White's January 2025 segmented anode bulletin and State's residential electric service handbook. Rheem's parts catalog publishes lengths of 42, 44, 54 and 58 inches, while Bradford White expects segmented rods to be cut to length in the field. - **Applies to:** Brand: Bradford White; Brand: Rheem and Ruud; Brand: A.O. Smith; Brand: State - **Compatibility basis:** Bradford White Product Department Bulletin of 14 January 2025 and electric service parts list 238-51592-00; Rheem Water Heater Parts and Accessories catalog; A.O. Smith instruction manual 185762; State service handbook 320990-000 and Powered Anode System user's guide 100305154 - **Assumptions:** Only Bradford White and Corro-Protec publish a thread size for the anode connection itself. The other makers print a socket size and part numbers but no NPT figure, so their cells read not published rather than an estimate.; The Rheem figures come from the Rheem Water Heater Parts and Accessories catalog, which is dated 2010 in the file and is the most recent Rheem-published anode dimension table found this session.; Whirlpool's own use and care guide was not readable at a citable URL this session, so no Whirlpool row appears. - **Method:** Thread sizes, lengths, part numbers, socket sizes, materials and service intervals copied from each manufacturer's own bulletin, parts list, manual or handbook. OwnerSpec pulled no anode rod and measured nothing. - **Primary source:** [Bradford White, Product Department Bulletin, New Product: Segmented Anode Rod Service Parts, 14 January 2025 (PDF)](https://bradfordwhitecorp.s3.us-east-1.amazonaws.com/wp-content/uploads/bwwh_bulletin_new_product_segmented_anode_rod_service_parts.pdf) (manufacturer or vendor document) - **Facts verified:** 2026-09-21 - **Last updated:** 2026-09-21 - **Canonical URL (cite this):** https://ownerspec.com/plumbing/parts/water-heater-anode-rod-by-model/ If your tank's hot outlet and its anode are one fitting, no plain replacement rod will go in, and that is the mistake this page exists to stop. ## Which anode fits your brand? Two numbers decide the part: thread and length. Only two makers print the thread for the anode connection. | Brand | Anode thread | Lengths published | Style on the tank | |---|---|---|---| | Bradford White | 3/4 in NPT, "intended to be used on any model with a ¾ inch NPT" | Not published: cut to length in the field. The outlet style ships with a 3 1/2 in nipple | Anode outlet device (AOD), or plug type into a separate port | | Rheem and Ruud | Not published in the parts catalog | 42 in (AP12938, aluminium), 44 in (SP11524C, magnesium), 58 in (SP11524Z), 54 in flexible (SP8371B) | Straight, or flexible in four 12 in sections | | A.O. Smith | Not published in the residential manual | Not published | Primary anode, plus a "Secondary Anode Rod/Nipple w/Heat Trap" on some electric models | | State | Not published in the service handbook | Not published | Stand-alone anode, or an anode combined with the outlet nipple | The hex head is the one dimension everyone agrees on. Rheem's parts catalog, dated 2010 in the file, lists 1-1/16 in for every anode it sells, and State's electric service handbook puts a "1 1/16 inch, 6 point, socket (for anode removal)" in its tool list. ## Magnesium, aluminium or powered? | Rod type | Buy it when | What the maker publishes | |---|---|---| | Magnesium | Default. The tank shipped with one and the hot water has no odour | Bradford White sells magnesium AOD 415-55482-00 and plug 415-55483-00 | | Aluminium or aluminium zinc | The hot water smells of rotten eggs | A.O. Smith: replace the anode with one of less active material, then chlorinate the tank and hot lines. It adds that this "may reduce but not eliminate water odor problems" | | Powered, impressed current | You are buying a sacrificial rod every year or two | Corro-Protec: 3/4 in NPT, 110 v socket, WQA certified against NSF/ANSI/CAN 372, conforms to UL Std. 1310, ETL Intertek 5003982 | State's handbook gives the field test: aluminium is "identifiable by smooth surface on plug", magnesium "by weld bead on plug". Aluminium has its own failure mode. Where the supply runs a relatively high pH (8 or above), State's handbook says it forms aluminium hydroxide, "jelly beads" or a gel in the heater drain and at faucet aerators, and that the fix "should only be performed by someone with abilities equal to a licensed tradesman". The chemistry behind the smell belongs to the [rotten egg smell guide](/water/guides/rotten-egg-smell-well-water/). This page picks the rod. ## Straight, segmented or combo? A straight rod needs its own length in clearance above the tank, so a 44 in Rheem SP11524C wants 44 inches of ceiling. Rheem's answer is the SP8371B, 54 in overall as "four 12 in. sections with flexible linkages", "for installations without the overhead clearance normally required for anode rod replacement". The Eastman 60286 listing prints 42 in and a 3/4 x 3 in NPT nipple. Bradford White's segmented parts are the same idea, "to provide additional flexibility in low clearance applications", and they "may also be cut to length based on the needs in the field". The combo rod is what catches people out. Bradford White: "The anode outlet device or AOD is a combination of the hot water outlet and anode rod, while the plug option is installed into a separate plug on the top of the water heater." If your tank has no separate anode port, a combo rod is the only part that fits, and a powered anode is out: State's guide requires a "stand-alone anode (i.e., the anode is not combined with an outlet nipple)" and a tank of 50 gallons or less. ## How often, and who should pull it? A.O. Smith's residential manual says to inspect the rod "after a maximum of three years and annually thereafter", and that "artificially softened water requires the anode rod to be inspected annually": see the [water softener size calculator](/water/calculators/water-softener-size-calculator/). Its two signs of a spent rod: most of the rod's diameter under 3/8 in, or "approx. 1/3 or more of the anode rod's length" of support wire visible. This is not a socket-and-go job. A.O. Smith's sequence begins with turning off the gas supply, shutting off the water, opening a hot faucet to depressurize the tank and draining approximately 5 gallons. Work from the manual for your model, and open the breaker first on an electric tank. A powered anode adds electrical work: State's guide requires installation to local and state codes or ANSI/NFPA 70 and a non-switched, powered outlet. A.O. Smith also states that leaving the tank with no rod voids all warranty on the tank. **Buy the socket before the rod** Check the port before ordering. If the only fitting on top is the hot outlet, you need a combo rod, not the Ozek segmented magnesium. If the hot water smells, the aluminium zinc rod is the cheap first move, and A.O. Smith's manual says it may not finish the job. After a second rod, the Corro-Protec powered anode ends the cycle on a tank of 50 gallons or less with a stand-alone port. ## The picks - **Eastman 60286 flexible magnesium anode rod**: Low ceiling above the tank, magnesium wanted (42 in flexible magnesium with a 3/4 x 3 in NPT stainless nipple, per the listing title; Eastman's own product page was not reachable this session) Amazon: https://www.amazon.com/dp/B09G3L9S17/?tag=ownerspec-20 - **Ozek 44 in segmented magnesium anode rod**: Like-for-like magnesium on a 44 in Rheem-length tank (44 in segmented magnesium per the listing title; thread size not printed in the title, so measure the port before ordering) Amazon: https://www.amazon.com/dp/B08HXBK6S5/?tag=ownerspec-20 - **Tandefio aluminium zinc anode rod, 3/4 NPT x 29 in**: The rotten-egg swap, with the thread actually published (3/4 in NPT, 29 in, aluminium zinc per the listing title; A.O. Smith warns a less active rod may reduce but not eliminate the odour) Amazon: https://www.amazon.com/dp/B0CWL151VR/?tag=ownerspec-20 - **Corro-Protec powered anode rod**: Readers replacing a sacrificial rod over and over (3/4 in NPT (1 in on the Buderus model), 110 v socket, WQA certified against NSF/ANSI/CAN 372, conforms to UL Std. 1310, ETL Intertek 5003982, per Corro-Protec's page; sold in tank-size variants, so pick the one matching your gallons on the listing) Amazon: https://www.amazon.com/dp/B06WP1VWWL/?tag=ownerspec-20 ## Frequently asked questions ### What thread size is a water heater anode rod? Bradford White's January 2025 bulletin states its segmented anode connections are 3/4 inch NPT and are intended for any model with a 3/4 inch NPT. Corro-Protec publishes 3/4 inch NPT for every residential powered model except its Buderus version, which is 1 inch NPT. Rheem, A.O. Smith and State publish a 1-1/16 inch hex head but no NPT figure. ### How do I tell a magnesium rod from an aluminium one? State's residential service handbook gives the field test on the plug itself: an aluminium anode is identifiable by a smooth surface on the plug, and a magnesium anode by a weld bead on the plug. Neither maker prints the material on the hex head, so the plug face is the only marking a reader can check without a part number. ### Which rod fits if there is no ceiling clearance above the tank? A segmented or flexible rod. Bradford White says its segmented rods were designed to provide additional flexibility in low clearance applications where a traditional solid rod is difficult to remove and install. Rheem's SP8371B is 54 inches made of four 12 inch sections with flexible linkages, sold for installations without the overhead clearance a solid rod needs. ### Can I fit a powered anode to any water heater? No. State's Powered Anode System user's guide limits the system to water heaters of 50 gallons or less, and requires the heater to have a stand-alone anode, meaning the anode is not combined with an outlet nipple. It must also stay plugged into a non-switched, powered outlet and be installed to local and state codes or ANSI/NFPA 70. ### How often should an anode rod be inspected? A.O. Smith's residential electric manual says the anode rod should be inspected after a maximum of three years and annually thereafter, and that artificially softened water requires annual inspection from the start. Its two signs of a spent rod are a majority of the rod's diameter under 3/8 inch, or support wire visible over approximately a third or more of the rod's length. ## Sources - [Bradford White, Product Department Bulletin, New Product: Segmented Anode Rod Service Parts, 14 January 2025 (PDF)](https://bradfordwhitecorp.s3.us-east-1.amazonaws.com/wp-content/uploads/bwwh_bulletin_new_product_segmented_anode_rod_service_parts.pdf) (manufacturer or vendor document) - [Bradford White, Electric Water Heater Service Parts List 238-51592-00 (PDF, anode outlet device and plug type part numbers)](https://docs.bradfordwhite.com/Parts_List/238-51592-00_Current.pdf) (manufacturer or vendor document) - [A.O. Smith, Instruction Manual, Residential Electric Water Heaters Models 6-120, document 185762 (PDF)](https://assets.hotwater.com/damroot/Original/10001/185762.pdf) (manufacturer or vendor document) - [State Water Heaters, Residential Electric Water Heater Service Handbook 320990-000 (PDF, socket size and the aluminium hydroxide technical bulletin)](https://assets.statewaterheaters.com/damroot/Original/10008/320990-000.pdf) (manufacturer or vendor document) - [State Water Heaters, Powered Anode System User's Guide 100305154 (PDF)](https://assets.statewaterheaters.com/damroot/Original/10009/100305154.pdf) (manufacturer or vendor document) - [Rheem, Water Heater Parts and Accessories catalog (PDF, distributor-hosted copy; anode rod length, diameter and hex head tables)](https://assets.unilogcorp.com/267/ITEM/DOC/Rheem_SP8346_Catalog.pdf) (manufacturer or vendor document) - [Corro-Protec, Powered Anode Rod product page (thread size, tank ranges, supply voltage and certifications)](https://corroprotec.com/products/powered-anode-rod) (manufacturer or vendor document) --- Citation: OwnerSpec, "Water Heater Anode Rod by Model: Which Thread, Which Length and Which of the Three Rod Types Fits Your Tank", https://ownerspec.com/plumbing/parts/water-heater-anode-rod-by-model/, facts verified 21 September 2026. 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