Radiator heat is part of Chicago’s architecture. Greystones, two-flats and courtyard buildings often run on steam, while many bungalows and single-family homes use hot water. Knowing which you have makes troubleshooting and repairs much easier.
How to tell them apart
| Steam | Hot water | |
|---|---|---|
| Boiler | Glass sight tube showing water level; low-pressure gauge (0–3 or 0–5 psi) | Pressure/temperature gauge around 12–25 psi; expansion tank; circulator pump |
| Radiators | Air vent on the side (one-pipe) or a trap at the outlet (two-pipe) | Small bleed screw near the top |
| Sounds | Hissing vents; banging if water pools | Gurgling if air is trapped |
How steam heat works
The boiler boils water, and steam rises through the pipes into the radiators, pushing air out through the vents. As it gives up its heat, the steam condenses back into water and flows back to the boiler. Pipes must slope correctly so the water drains; when they sag, water collects and causes the banging known as water hammer.
How hot-water heat works
A hot-water boiler heats water and a circulator pump moves it through the radiators in a closed loop. The expansion tank absorbs the water’s growth as it heats. Air in the system collects at the top of radiators, which is why bleeding matters.
Common problems
- Steam: clogged radiator vents, half-open valves, banging pipes, low water, dirty boiler water causing surging.
- Hot water: trapped air, low or rising pressure, a waterlogged expansion tank, failed circulators and stuck zone valves.
Replacing an old boiler
Cast iron boilers often last 20 to 35 years or more. A steam system needs a steam boiler, sized to the radiators it serves. A hot-water system can often move to a high-efficiency condensing boiler, which works best with lower water temperatures. Either way, sizing should come from the radiators and the house, not just the old boiler’s label.
For repairs or replacement, see boiler repair in Chicago or call (312) 924-7223.