Six water heater parts account for ~90% of all replacements: the anode rod, heating elements (electric tanks), thermostats, pressure relief (T&P) valve, expansion tank, and dip tube. Most are DIY-replaceable with basic tools. This page maps the parts to symptoms and links to dedicated guides.
The water heater parts catalog
- Anode rod — sacrificial rod that protects the tank from corrosion. Replace every 4-7 years. The single highest-ROI water heater part — extends tank lifespan by 4-8 years
- Heating element — on electric tanks only. Upper and lower elements; either can fail. $25-60 parts, DIY-replaceable
- Thermostat — controls temperature on electric tanks (upper and lower thermostats). $30-70 parts
- Pressure relief (T&P) valve — safety device that opens at 150 psi or 210°F. Test annually; replace if it drips
- Expansion tank — small bladder tank that absorbs thermal expansion in closed plumbing systems. Required by code in most new installs
- Dip tube — plastic tube that routes cold inlet water to the bottom of the tank. Broken dip tube = hot water runs out fast
- Drain valve — bottom of tank. Replace with a brass ball valve if the original is plastic
- Gas control valve — gas units only. Modulating solenoid plus pilot/igniter logic. Dealer-only replacement
- Thermocouple / flame sensor — gas units. Pilot/flame detection. See brand-specific parts pages for tankless: Rinnai flame rod, Navien flame rod
Symptom to part mapping
| Symptom | Likely part |
|---|---|
| Rotten egg smell | Anode rod (replace with aluminum-zinc) |
| Rusty hot water | Anode rod consumed; tank may also be corroding |
| Hot water runs out fast | Dip tube (broken) or sediment-filled tank |
| No hot water (electric) | Upper thermostat or upper element, or tripped breaker |
| Lukewarm water (electric) | Lower thermostat or lower element |
| Pilot won't stay lit | Thermocouple; on Bradford White also intake filter |
| T&P drips constantly | T&P valve seat fouled, OR expansion tank bladder failed |
| Water hammer / pulsing pressure | Expansion tank missing or failed |
| Popping / rumbling noise | Sediment (flush) — see popping noise |
Universal vs OEM parts
Most tank water heater parts are largely standardized:
- Anode rods: standard ¾" NPT thread, available in 32"-44" lengths. Aftermarket (Camco, Suburban) works as well as OEM
- Heating elements: standard 1" NPS screw-in OR 4-bolt flange (older units). 240V, typically 4500W upper / 4500W lower
- Thermostats: brand-cross-referenced. Honeywell, White-Rodgers, Robertshaw drop in to most major brands
- T&P valves: standard ¾" NPT, set to 150 psi / 210°F. Watts, Cash Acme, Reliance
- Expansion tanks: standard threaded connection (½" or ¾"). Watts, Amtrol, Zilmet
Tankless parts are more brand-specific — flame rods, igniters, control boards, gas valves vary by manufacturer and model. Use brand-specific parts pages.
Parts and warranty
Inside the unit's parts warranty (typically 5-10 years on most brands), Replacement parts are supplied by the manufacturer at no cost to the homeowner — but only when installed by an authorized installer. DIY replacement of warranty-period parts voids the warranty for the affected system. Out of warranty, DIY with aftermarket parts is fine.
By-brand parts directories
Related guides
Bottom line
Most water heater repairs come down to one of six parts. Anode rod is the single highest-ROI replacement — DIY it every 4-6 years and you'll extend tank lifespan by 4-8 years. Elements and thermostats on electric tanks are also routine DIY swaps. Anything on the gas side beyond the thermocouple, hire a plumber.