Boiler Parts That Fail Most Often — Replacement Guide

Published: July 22, 2026 — CANRO Heating & Cooling — Greater Vancouver, BC

1. Expansion Tank — Most Common Failure

The expansion tank bladder fails after 5-10 years, causing pressure fluctuation and PRV discharge. Replacement cost: $250-600. Symptoms: pressure rises rapidly when the boiler fires, PRV drips water. This is the most common boiler issue we encounter.

2. Circulation Pump — Second Most Common

Circulation pump failures cause no heat. The pump may make noise, leak water from the shaft seal, or simply stop running. Replacement cost: $400-900. Grundfos pumps are the most common and readily available. Most replacements are completed same-day.

3. Zone Valve — Common in Multi-Zone Systems

Zone valves fail on the motor or the internal mechanism, causing loss of heat in one zone. Replacement cost: $300-600 per valve. If one zone valve fails, others in the system may follow — consider proactive replacement of all zone valves when one fails.

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Safety Reminder

If you smell gas, suspect carbon monoxide or believe there is an immediate danger, leave the property and contact emergency services or the appropriate gas emergency authority. Do not remain inside — exit the building immediately and call for help from outside.