Why Is My Boiler Hot Water Warm But Not Hot?

Published: July 21, 2026 — CANRO Heating & Cooling — Greater Vancouver, BC

Combi-Boiler Hot Water Issues

If central heating works but hot water is only warm, the issue is in the domestic hot water (DHW) system. Common causes: a failed diverter valve that is not switching from heating to hot water mode, a faulty DHW thermistor giving incorrect temperature readings, or a blocked plate heat exchanger from scale buildup.

Temperature Setting Check

Verify the DHW temperature setting on the boiler control panel. Typical setting is 120°F (49°C). If it is set lower, increase and test. Some boilers have separate settings for heating and hot water temperatures.

Professional Diagnosis

If temperature settings are correct, professional diagnosis is needed. Scale buildup in the plate heat exchanger is the most common cause in Vancouver — descaling restores full hot water temperature. Diverter valve replacement costs $300-600.

Related Services

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.