Thermal expansion tank installation
A thermal expansion tank gives heated water somewhere to expand when a check valve, pressure-reducing valve or backflow preventer keeps it from pushing back into the supply. Without one, pressure builds until the relief valve opens. North Carolina code requires one on storage water heaters in those systems.
Water expands as it heats. In an open system it pushes back toward the street, but many homes now have a check valve, pressure-reducing valve or backflow preventer on the supply, which makes the system closed.
In a closed system, every heating cycle raises pressure. The signs are a relief valve that drips after heating, banging pipes and pressure spikes that wear out fixtures.
Signs you need expansion tank installation
- Relief valve drips after the heater runs
- Pressure that climbs at night
- A pressure-reducing valve or backflow preventer on the supply
- Installing or replacing a storage water heater
How expansion tank installation is done
- 1
Check the system
Measure pressure and identify check, PRV or backflow devices.
- 2
Size and pre-charge
Size the tank for the heater and set its air charge to match house pressure.
- 3
Install and support
Install on the cold supply near the heater, properly supported.
What affects the cost of expansion tank installation
- Tank size
- Access to the cold supply
- Whether it's added to an existing heater or part of a replacement
Ask for the trip fee and the total price before work starts.
Need expansion tank installation? Call now
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Expansion tank installation: common questions
Does my water heater need an expansion tank?
If your supply has a check valve, pressure-reducing valve or backflow preventer, North Carolina code requires one with a storage water heater, including on replacements.
Why does the air charge matter?
The tank's air charge should match the house water pressure, or it won't absorb expansion properly.
How long do expansion tanks last?
Several years; a waterlogged tank (one that sounds full when tapped at the top) has lost its air bladder and needs replacement.