Boiler Radiators Cold Upstairs in Greater Vancouver

Cold radiators on the upper floor of a Greater Vancouver home while lower floors heat normally is a common hydronic system issue — and it is usually related to air accumulation or circulation balance, not a boiler fault.

What This Symptom Means

Hot water rises in a hydronic system, but air accumulates at the highest points of the system — often in upper floor radiators and the pipes feeding them. Air blocks water flow and prevents heat from reaching those radiators.

Common Causes

• Air accumulated in upper floor radiators — very common in two-storey homes
• Insufficient water pressure for upward circulation to upper floors
• Zone valve not opening for upper floor zone
• Circulator pump undersized for the height of the system
• Upper floor radiators not sized correctly for the room heat load
• Balancing valves not adjusted to ensure upper floor receives adequate flow

What Homeowners Can Check Safely

• Bleed upper floor radiators — use the bleed key on the radiator bleed valve (small valve at top or side of radiator) until water runs steadily and no air hisses out
• Repeat for all upper floor radiators
• After bleeding, check system pressure and add water if below 12 psi

When to Call a Licensed Technician

Boiler systems involve pressurized hot water, gas, and electrical components. Do not attempt to open sealed components, adjust gas pressure, or bypass safety controls without professional diagnosis.

• System-wide bleeding and air purging
• Balancing valve adjustment to direct more flow to upper floors
• Expansion tank and automatic air vent inspection
• Zone valve testing for upper floor zone
• Pump head pressure assessment to confirm pump can serve system height

Frequently Asked Questions

How do I bleed a radiator?

Use a radiator bleed key (a small square tool that fits into the bleed valve, usually at the top corner of the radiator) or a flathead screwdriver. Turn the valve counterclockwise slowly — air will hiss out first, followed by water. When water runs steadily with no air bubbles, close the valve. Have a cloth ready to catch drips. Do this for each upper floor radiator.

How often do radiators need to be bled?

In a well-maintained system with an automatic air separator, manual bleeding should rarely be needed. If you find yourself bleeding the same radiators repeatedly, air is continuously entering the system — usually from a leak drawing in air, a failing automatic air vent, or a system that was not properly purged after water was added.

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