THE SHORT VERSION
- Gas or electric tank: flush sediment and test the relief valve lever at least yearly, and have the anode rod checked. A.O. Smith says flush every 6 months; Rheem says yearly, or every 6 months in hard water. Your manual wins.
- Gas tanks also need air: look at the burner and vent yearly, vacuum lint from the air intake, keep flammables out of the room.
- Tankless: a yearly professional service, with descaling in hard water. Rinnai, Navien and Rheem exclude scale damage from their warranties; Rheem’s requires hardness of 200 mg/L or less.
- Heat pump: the tank jobs, plus an air filter Rheem says to check monthly and a condensate line that must stay clear.
- Leave to a pro: anode swaps, burners, gas lines, vents, wiring and refrigerant. HomeAdvisor’s survey puts a professional flush at $110–$200.
The master schedule
This table collects every routine task in the manuals and maintenance guides of Rheem, A.O. Smith, Rinnai and Navien, plus the relief valve and expansion tank makers. “You” means a homeowner can do it safely by following the manual; “Pro” means a licensed plumber or service technician, for reasons explained below.
| Task | Heater types | How often | Who | Source |
|---|---|---|---|---|
| Look-around: water on the floor or in the pan, rust, damp fittings, odd noises, error codes | All | Monthly | You | Rheem |
| Test the relief valve lever | Tanks, heat pump | At least yearly; A.O. Smith’s gas manual says every 6 months | You, with care, or pro | Watts, Rheem, A.O. Smith |
| Relief valve removed and inspected | Tanks, heat pump | Every 2–4 years | Pro | Watts |
| Flush sediment from the tank | Tanks, heat pump | Every 6–12 months; every 6 in hard water | You or pro | A.O. Smith, Rheem |
| Inspect the anode rod | Tanks, heat pump | First at 6–12 months, then yearly; no later than every 3–4 years | Pro | A.O. Smith, Rheem, DOE |
| Look at the burner flame and vent for soot, rust or damage | Gas tank | Yearly | You look; pro fixes | A.O. Smith |
| Vacuum lint at the base and air intake; keep flammables away | Gas tank (FVIR models) | Regularly (no interval given; every few months is sensible) | You | A.O. Smith |
| Clean the burner, combustion chamber or flame arrestor; draft test | Gas tank | Yearly, or when soot or pilot outages appear | Pro | Rheem, Bradford White |
| Inspect controls, elements and wiring | Electric tank, heat pump | Periodically | Pro | Rheem |
| Clean the inlet water filter | Tankless | Yearly, more often with gritty water | You | Rheem, Rinnai |
| Clean the combustion air filter | Indoor gas tankless | Every 3–4 months (Navien); when dirty (Rinnai) | You | Navien, Rinnai |
| Descale (flush) the heat exchanger | Tankless | At least yearly; about every 6 months in hard water | Pro recommended | Rinnai, Rheem |
| Annual inspection: burner, vent, condensate neutralizer | Gas tankless | Yearly | Pro | Rinnai, Rheem |
| Check the air filter and condensate drain | Heat pump | Monthly | You | Rheem |
| Clean the evaporator coil | Heat pump | When dirty | Pro | A.O. Smith |
| Check the hot water temperature | All | Yearly, and after any change | You | Rheem, CPSC |
| Check the expansion tank’s air charge | Any heater on a closed system | Yearly | Pro, at a service visit | Zurn |
| Test the carbon monoxide alarm | Gas heaters | Monthly; new batteries yearly | You | Rinnai |
Sources: manufacturer manuals and guides listed at the end of this page. Intervals are the manufacturers’, not ours. FVIR means flammable vapor ignition resistant: gas tanks with a flame arrestor that keeps vapors from reaching the burner.
Where manufacturers disagree, and what to do
Intervals differ between brands, and sometimes between documents from the same brand. The disagreement is about how cautious to be, not about what the jobs are.
| Source | Flush sediment | Anode rod |
|---|---|---|
| A.O. Smith gas tank manual (2021) | Every 6 months | Inspect after 6 months, then yearly; more often with a softener |
| A.O. Smith heat pump service handbook (2024) | After 6 months, then at least yearly | Same as flushing |
| Rheem electric tank manual | Drain a few quarts every month | Remove and inspect yearly; replace when more than 6 inches of core wire shows |
| Rheem maintenance guide (2025) | Yearly; about every 6 months in hard water | Check yearly |
| Rheem lifespan article (2026) | Yearly | Replace every 3–4 years |
| DOE Energy Saver | — | Inspect every 3–4 years |
Sources: A.O. Smith manual 100341468 and hybrid handbook 2000620230; Rheem manual AP21980 and articles (December 2025, March 2026); DOE Energy Saver (archived May 2026).
How to choose:
- Your manual first. Rheem’s tank warranty excludes failures from “failure to operate and maintain the water heater in accordance with the manufacturer’s instructions.”
- Hard water or a softener puts you at the short end. Rheem says flush about every six months in hard water; A.O. Smith says softened water uses up the anode faster.
- Check the anode early once. How fast your first rod wears tells you more about your water than any table.
Jobs you can do, and jobs for a pro
Safe owner jobs, in summary
The monthly look-around
Two minutes with a flashlight: the floor and pan, the fittings on top, the relief valve pipe, rust at the base, the display for error codes. Rheem suggests a monthly visual check for leaks, corrosion or wear.
Test the relief valve
Check that the discharge pipe ends somewhere safe and no one is near it, lift the lever for a few seconds, and let it snap shut. If no water flows, Watts says turn the heater off and call a plumber; if it won’t stop, A.O. Smith says close the cold inlet and have the valve replaced. Details in relief valve leaking.
Flush the tank
Turn the breaker off on an electric heater (Rheem) or follow your manual for the gas control, run a hot tap until the water cools, and drain through a hose to a floor drain. Full steps in how to flush a water heater.
Clean filters and check the temperature
Filters on tankless and heat pump units take minutes with the power off (see the type sections). For temperature, hold a kitchen thermometer under the nearest hot tap, as CPSC suggests.
Jobs for a licensed pro, and why
- Anode rod. It is screwed tightly into the top of the tank; removal means shutting off the water, partly draining and resealing. Rheem says anode and relief valve work is often “best handled by a qualified plumber.” See anode rods.
- Burner, flame arrestor and draft. Bradford White’s arrestor cleaning starts by disconnecting the burner feed line and is for “qualified service providers” only. A draft test is venting work.
- Elements, thermostats and wiring. Rheem assigns these to service personnel qualified in electric appliance repair.
- Tankless descaling. Rinnai says it “should be completed by a professional installer.” Navien gives an owner procedure but calls it “somewhat complicated.”
- Heat pump coil and refrigerant, relief valve inspection, expansion tank charge and pressure regulators: these need panels off or the system depressurized.
Flushing: sediment is what a tank collects
Minerals drop out of water as it heats and settle on the tank bottom, under a gas burner’s heat or around an electric tank’s lower element. Rheem says sediment reduces efficiency, causes rumbling and can lead to corrosion and leaks. OSHA adds that heaters kept below 140°F that contain scale and sediment may foster Legionella bacteria, a concern it raises for larger systems.
A.O. Smith flushes with the cold supply left on, so incoming pressure stirs the bottom and carries sediment out the drain valve until the water runs clear. Rheem’s electric manual drains a few quarts every month. The full procedure is in how to flush a water heater.
The anode rod: the part that decides how long a tank lasts
A tank is glass-lined steel, and the anode rod, usually magnesium or aluminum, is slowly consumed to protect it (Rheem). A.O. Smith says it helps reduce corrosion and premature leaks, and Rheem says checking it annually “can add years to your water heater’s lifespan.”
- When: A.O. Smith says after the first six months, then yearly. Rheem says yearly, and replace the rod when more than 6 inches of its steel core wire shows.
- Softeners use rods faster, so A.O. Smith says inspect more often.
- Rotten-egg smell: Rheem says it may mean bacteria reacting with a magnesium anode, and suggests an aluminum or powered anode.
- Never run without one. Rheem and A.O. Smith both void or exclude tank coverage if the anode is removed; A.O. Smith doesn’t cover the rod itself.
Rod types, replacement and the clearance a rod needs above the tank are in anode rods.
Gas tanks: the burner needs clean air
Modern gas tanks are flammable vapor ignition resistant (FVIR). A.O. Smith explains that combustion air passes an air filter and a flame arrestor, which helps keep vapors in the room from being ignited. The arrestor is a fine screen or ceramic plate that clogs with lint, and A.O. Smith says frequent pilot outages or a tripped thermal switch often mean the heater isn’t getting enough air.
- Vacuum the base for dust and lint on a regular basis, and the air filter from time to time (A.O. Smith). Laundry rooms need it most.
- Keep the space clear: nothing stored against the heater and no gasoline, solvents or paint in the room. A.O. Smith warns that spray cans, bleach, pool chemicals and refrigerants also corrode the flue and vent.
- Look once a year at the burner flame for soot and the vent for blockages, damage and rust flakes on top of the heater. A.O. Smith says soot is not normal: turn the gas off and call for service.
- Don’t cover air openings. With an insulating blanket, Rheem says leave the burner access and air intake uncovered.
Tankless: scale is the main job
A tankless heater has no tank and no anode, but its narrow heat exchanger passages scale up fast in hard water. Rinnai says scale “can be accelerated if the water heater is set at a high temperature” and that lime damage isn’t covered by its warranty.
- Descaling: Rinnai says at least once a year, by a professional; Rheem says yearly, about every six months in hard water. A pump circulates vinegar or descaler through the service valves for 45–60 minutes (Navien, Rinnai). Full guide: descaling a tankless water heater.
- Inlet water filter: a small screen where cold water enters. Rinnai: close the isolation valves, bucket underneath, unscrew and rinse.
- Air filter (indoor gas units): Navien says clean it every 3–4 months; when clogged, the heater stops with an error code.
- Vents: Navien says inspect the termination and air intake yearly; Rinnai says keep them clear of snow and ice.
- Annual inspection: Rinnai says the unit “must be inspected annually by a trained and qualified professional”: burner flame, vent, condensate and, on condensing models, the neutralizer Rheem says to check yearly.
Electric tankless units are simpler. Rheem asks owners to inspect the inlet and outlet connections yearly and to treat hard water or flush regularly. After any plumbing work that lets air into the pipes, turn the breaker off and run the taps to purge air before restoring power; Rheem says skipping this can ruin the elements and void the warranty.
Heat pump: a tank plus a filter and a drain
A heat pump water heater is an electric tank with a heat pump on top, so it needs every tank job, plus two small owner jobs.
- Air filter: Rheem says check it monthly and wash it with mild soap and water; A.O. Smith says at six months, then at least yearly. Models built to NEEA’s higher tiers remind you.
- Condensate drain: Rheem says check it monthly; A.O. Smith says clean the pan yearly. On models built to NEEA’s specification a blocked drain shuts the compressor off, so a unit suddenly running on its elements may just have a clogged line.
- Clearance: Rheem says keep 18–24 inches clear around the unit.
- Pro visit: Rheem recommends a yearly visit to flush the tank, test the relief valve and inspect electrical connections.
Temperature: start at 120°F
CPSC urges households to set water heaters to 120°F, and A.O. Smith calls 120°F the preferred starting point; Rheem says 120–125°F. CPSC says most adults suffer third-degree burns in 2 seconds at 150°F, 6 seconds at 140°F and 30 seconds at 130°F. Lower settings also slow scaling.
The trade-off is Legionella: OSHA says heaters kept below 140°F that contain scale and sediment may foster it, mainly a concern for large systems. Some households with high-risk members run a hotter tank with mixing valves at the taps. See what temperature to set a water heater.
Expansion tanks, pans and leak sensors
A house with a check valve, backflow preventer or pressure regulator on the main is a closed system and needs an expansion tank. Zurn says check its air charge yearly with the water pressure removed, and replace the tank if it reads zero or water comes out of the air valve. A.O. Smith says a relief valve that weeps periodically may mean thermal expansion isn’t being controlled.
- Drain pan: keep it empty and its drain clear. On gas heaters, A.O. Smith says the pan must not restrict combustion air.
- Leak sensors: A.O. Smith mentions pan sensors that sound an alarm or shut off the water; Rheem’s LeakGuard valve tests itself every 30 days. Battery sensors need fresh batteries.
- Attics and closets over finished floors: check whether your code requires a pan; see code requirements.
What the warranty actually requires
None of the documents we read asks for proof of a yearly flush. They exclude the damage skipped maintenance causes, so a scaled heat exchanger or a tank run without its anode becomes your bill. Navien also excludes “failure to perform regular maintenance” outright.
| Document | What it says about maintenance |
|---|---|
| Rheem tank warranty (AP16695-2) | Excludes failures from not maintaining the heater per the manufacturer’s instructions, or running it with the anode removed |
| A.O. Smith gas tank manual | Removing the anode voids the tank warranty; anodes are consumables; relief valve leakage on a closed system without an expansion tank isn’t covered |
| Rheem gas tankless warranty (AP21265) | Excludes damage where water exceeds its limits, including hardness over 200 mg/L, and damage from lime, mineral build-up or scale |
| Rinnai tankless manual | Lime and freeze damage not covered; must be inspected annually by a trained professional |
| Navien tankless warranty | Excludes failure to perform regular maintenance, hard water deposits, lime and mineral build-up, and freeze damage |
| Rheem electric tankless manual | May deny claims for water outside its limits; element damage from not purging air voids the warranty |
Terms vary by model and change over time; Rheem’s tank certificate read here dates from 2014. Read the certificate for your exact model number. More in water heater warranties.
What a professional service visit should include, and cost
Ask for the work by name: “water heater service” can mean a 20-minute drain or a full inspection.
A complete service visit
- Every type: relief valve tested; leaks, pan and connections checked; temperature measured; water pressure and expansion tank charge checked
- Tanks: flushed until clear; anode pulled and shown to you
- Gas tanks: burner, pilot, flame arrestor and air intake cleaned or checked; vent and draft checked
- Electric tanks: elements and wiring connections inspected
- Gas tankless: descaled; filters cleaned; burner flame, vent, condensate and neutralizer checked
- Heat pump: tank jobs plus filter, condensate drain and coil
| Job | Typical range | Notes |
|---|---|---|
| Professional flush, any type | $110–$200 | Average $160; as low as $75 and as high as $250 |
| Tank flush | $75–$150 | Larger tanks take longer |
| Tankless flush (descaling) | $150–$250 | Pump, hoses and descaler |
| Anode rod replacement | $50–$150 | Parts and labor |
| Relief valve replacement | $20–$200 | Parts and labor |
Source: HomeAdvisor flush and repair cost guides (updated June 2026). HomeAdvisor is a lead-generation site and these are its survey ranges, not quotes. Some plumbers charge a flat $100–$400 or a minimum trip fee, per the same guide; bundling jobs in one visit saves trip charges.
Yearly maintenance plans from plumbers and utilities are worth pricing against this list. On a tank past 10 years, the money may do more toward a planned replacement; see repair or replace.
Vacation and seasonal settings
| Heater | Away a few days to weeks | Long shutdown or freezing risk |
|---|---|---|
| Gas tank | VAC setting; A.O. Smith’s holds about 55°F | Gas off at the heater’s shutoff; drain if it may freeze (A.O. Smith) |
| Electric tank | Vacation mode, or turn the thermostat down | Power and water off; drain if it may freeze (Rheem) |
| Heat pump | Vacation mode: A.O. Smith’s holds 50°F for 1–99 days; Rheem’s runs 2–28 days or indefinitely | As for an electric tank |
| Tankless | Nothing; it heats only on demand | Drain it if it won’t be used in freezing weather (Rinnai); Rinnai and Navien exclude freeze damage |
Sources: A.O. Smith and Rheem manuals and spec sheets; Rinnai and Navien manuals. Mode names vary by model.
Rheem suggests spring or fall for the yearly service. Before winter, clear snow from tankless vent terminations and make sure any heater in a garage, crawlspace or outdoor closet is protected from freezing.
The printable checklist
Monthly (5 minutes)
- No water on the floor, in the pan or at the relief valve pipe
- No rust at the base or top; no damp or crusty fittings
- No new rumbling or popping; no error codes
- Heat pump: filter clean, condensate line draining
- Gas: base and intake free of lint, nothing flammable nearby, CO alarm tested
Every 3–6 months
- Indoor gas tankless: clean the air filter
- Gas tank: vacuum the base and air intake
- Hard water or a softener: flush the tank or descale the tankless unit
Yearly
- Relief valve lever tested; tank flushed; anode inspected
- Gas tank: burner flame and vent looked at
- Tankless: professional inspection and descaling; inlet filter cleaned
- Hot water temperature measured; expansion tank charge checked
- CO alarm and leak sensor batteries replaced
Every 2–4 years
- Relief valve removed and inspected by a plumber (Watts)
- Anode replaced if worn; Rheem and DOE’s 3–4 years is the outer limit
Common questions
How often should a water heater be serviced?
At least once a year for every type. Tanks need a flush, a relief valve test and an anode check; Rinnai requires a yearly professional inspection of its tankless units; heat pump models add a monthly filter check. Hard water shortens every interval.
Is it bad to never flush a water heater?
It costs efficiency and tank life, especially in hard water; Rheem links sediment to rumbling, corrosion and leaks. On an older tank that has never been flushed, open the drain valve gently, or have a plumber do the first flush.
Do tankless water heaters need maintenance?
Yes. Rinnai and Rheem call for descaling at least yearly, more often in hard water, plus cleaning the inlet filter and checking vents and condensate. Rinnai, Navien and Rheem all exclude scale damage from their warranties.
How often do you clean a heat pump water heater filter?
Rheem says check it monthly and wash it with mild soap and water when dusty. A.O. Smith gives six months, then at least yearly, as the minimum.
Can I check the anode rod myself?
Some owners do, but it means shutting off the water, partly draining the tank and breaking a very tight fitting, then resealing it. We list it as plumber work, often done during a flush visit. HomeAdvisor’s survey puts a replacement at $50–$150 installed.
Does skipping maintenance void a water heater warranty?
It can void coverage for the damage it causes. Rheem’s tank warranty excludes failures from not maintaining the heater per its instructions, and Rheem, Rinnai and Navien tankless warranties exclude scale damage. Keep receipts.
What should I do with my water heater when I go on vacation?
Use the vacation setting on a tank or heat pump model; a tankless unit needs nothing. Drain any heater that could freeze while you’re gone. After two weeks or more, Rheem says run the kitchen hot tap for several minutes before using hot water appliances.
Sources
Sources checked October 4, 2026. Prices, codes and rebates change. Check current details with your installer and local permit office.
- Signature 100 series high-recovery gas water heater installation instructions and use & care guide 100341468 (March 2021) ↗ · A.O. Smith
- Cleaning the air filter and flame arrestor ↗ · A.O. Smith
- Residential hybrid electric heat pump water heater service handbook 2000620230 Rev D (2024) ↗ · A.O. Smith, hosted by State Water Heaters
- How to keep your tank and tankless water heaters running at peak performance (December 2025) ↗ · Rheem
- Heat pump water heater maintenance: complete Rheem care guide (September 2025) ↗ · Rheem
- Water heater lifespan: when to repair vs. replace (March 2026) ↗ · Rheem
- Performance Platinum electric water heater use & care manual AP21980 Rev 02 ↗ · Rheem
- ProTerra hybrid electric heat pump with LeakGuard spec sheet ↗ · Rheem
- Residential gas or electric water heater limited warranty AP16695-2 (2014) ↗ · Rheem, hosted by Home Depot
- Residential tankless gas water heater limited warranty AP21265 ↗ · Rheem
- Electric tankless water heater installation instructions and home owners manual ↗ · Rheem
- FVIR gas water heater service manual 238-51542-00A (2015) ↗ · Bradford White, hosted by G.T. Sanders
- SENSEI RSC tankless water heater installation and operation manual 100000773 ↗ · Rinnai
- CX series condensing tankless installation and operation manual ↗ · Rinnai, hosted by Lowe’s
- Residential tankless FAQ ↗ · Rinnai
- NPE-2 condensing water heater user’s information manual ↗ · Navien
- NPE-A2 series limited warranty ↗ · Navien
- Series LF1L, LF1XL, LF10L and LF100XL T&P relief valves spec sheet (2014) ↗ · Watts, hosted on Cloudinary
- Model XT thermal expansion tanks installation and maintenance instructions ↗ · Zurn Wilkins, hosted on Cloudinary
- Advanced Water Heating Specification, version 8.1 ↗ · Northwest Energy Efficiency Alliance (NEEA)
- Storage Water Heaters (archived copy, May 2026) ↗ · U.S. Department of Energy, Energy Saver
- Avoiding Tap Water Scalds (document 5098) ↗ · U.S. Consumer Product Safety Commission
- Legionnaires’ disease: control and prevention ↗ · U.S. Occupational Safety and Health Administration
- Water heater repair cost guide (updated August 2025; lead-generation site) ↗ · Fixr
- How much does it cost to flush a water heater? (updated June 2026; lead-generation site) ↗ · HomeAdvisor
- Water heater repair cost guide (updated June 2026; lead-generation site) ↗ · HomeAdvisor