Key Takeaways. The average cost of a water heater expansion tank is between $90 and $350, with the average cost being $220.; Water heater expansion tanks typically vary in size from 2 to 5 gallons ...

People got Dan’s concept a little misconstrued, because they thought the boiler was the PONPC. And if the expansion tank is connected to the boiler, that statement is true. In newer systems, the ...