Expansion tank replacement cost
Expansion tank installation cost averages $325 for a water heater in 2026, with most homeowners paying $150 to $450, according to Angi. Replacing an existing tank typically runs $90 to $350.
| New installation (Angi, avg $325) | $150–$450 |
| Replacement incl. labor (Angi) | $90–$350 |
| Labor only (Angi) | $50–$150 |
| Thermal expansion tank, part (Angi) | $40–$200 |
| 2-gallon tank, part (Angi) | $40–$60 |
| 4-gallon tank, part (Angi) | $60–$90 |
| Reinspection fee if missed (Angi) | $25–$100 |
Why expansion tanks are required
Water expands as it heats. In a closed system, where a pressure regulator or backflow preventer stops water from flowing back to the street, that extra volume has nowhere to go. Angi notes codes typically require an expansion tank on closed systems, and some water heater warranties require one. Tankless heaters do not need one.
Sizing
Tank size depends on water heater capacity and incoming pressure. Angi's guide suggests, for example, a 2-gallon tank for a 40- to 60-gallon heater at 40 to 50 PSI, and larger tanks as pressure rises.
Signs your expansion tank has failed
- The relief valve on the water heater drips.
- The tank sounds full of water when tapped (it should sound hollow at the top).
- Rust or drips at the tank connection.
Angi says tanks commonly need replacement every five to ten years.
Install it with related work
A plumber replacing a water heater or pressure regulator can add the tank for little extra labor. City permit fees for water heater work vary widely; Angi reports $100 to $1,500 depending on location, so ask your plumber what applies locally.
Frequently asked questions
How much does it cost to install an expansion tank on a water heater?
Angi's 2026 average is $325, with most homeowners paying $150 to $450.
How much does it cost to replace an expansion tank?
Angi lists replacement at $90 to $350 including labor.
Is an expansion tank required by code?
Typically on closed systems with a pressure regulator or backflow preventer, per Angi; check local code.
Does a tankless water heater need an expansion tank?
No. Angi notes tankless water heaters do not require one.
Related cost guides
- Water heater replacement cost
- Water heater repair cost
- Water pressure regulator replacement cost
- Backflow preventer replacement cost
Sources
National figures from published 2026 cost guides, retrieved 10 Oct 2026. Local prices, especially in high-cost metros, can be higher. Always get written quotes.