Boilers heat a huge share of older Chicago homes, from bungalows to greystones and courtyard buildings. When the boiler runs but radiators stay cold, the fix depends on whether you have hot water or steam. If you’re not sure, our boiler repair page shows how to tell.
Hot-water systems
Trapped air
Radiators that are warm at the bottom and cold at the top usually have air trapped inside. Bleeding them releases it; see how to bleed a radiator.
Low system pressure
A hot-water system needs enough pressure to push water to the top floor, typically around 12 to 15 psi cold in a two-story home. If the gauge reads low, water isn’t reaching upstairs radiators. Pressure that keeps dropping means a leak.
Circulator pump
The circulator moves water through the system. If it has seized or failed, the boiler gets hot but nothing moves. Sometimes you can feel the pump body for vibration; a technician can confirm.
Zone valves
Homes and two-flats with several zones use motorized valves. A stuck valve leaves one zone cold while the rest heat normally.
Steam systems
Clogged radiator air vents
On one-pipe steam, each radiator has an air vent that lets air out so steam can come in. A clogged vent keeps that radiator cold. Replacing the vent is often the fix.
Valves partly closed
One-pipe steam radiator valves must be fully open or fully closed. Half-open valves block steam and trap water, causing cold radiators and banging.
Low water or no steam
Check the sight glass on the boiler. If the water is very low or the boiler isn’t building steam, the low-water cutoff may be shutting it down. Turn the boiler off and let it cool before adding water; never add cold water to a hot, dry boiler.
Main vents
Large vents on the steam mains in the basement let air escape so steam can travel quickly. Failed main vents make the far radiators slow to heat.
When to call
If bleeding or checking valves doesn’t solve it, or the pressure or water level keeps dropping, call (312) 924-7223 for boiler repair in Chicago.