Boiler repair or replacement: how to decide

By GW Mechanical Corp. Published October 4, 2026.

When a boiler fails in the middle of winter, the first question is whether to fix it again or replace it. Here is how to decide, without guessing.

Replace when one of these is true

• The heat exchanger or a cast-iron section is cracked. This cannot be reliably repaired, and a cracked exchanger can leak flue gas.
• Repairs are adding up. Three or more significant repairs in one season usually means the boiler is wearing out as a whole.
• The repair costs a large share of a new boiler. A common rule of thumb: when a single repair approaches half the cost of replacement on an older boiler, replacement is the better spend.
• Parts are no longer available for the model, or only through salvage.

Repair when these are true

• The boiler is under about 15 years old and the failure is one part: an ignitor, thermocouple, flame sensor, gas valve, circulator or control.
• The boiler has been reliable and maintained, and this is the first significant problem.
• Combustion and venting test clean.

Comparing the two

Steam buildings are different

If your building has steam radiators, the replacement has to be a steam boiler. Many complaints blamed on an old steam boiler are really failed vents, poor pipe pitch or water level problems, which a good repair visit can fix without replacing the boiler.

We give an honest recommendation either way. Start with boiler repair, or see what goes into a boiler replacement.

Questions