Steam Boiler Repair and Steam Heat Service in Chicago

What we check on a steam boiler repair call

We start at the boiler and work outward. The sight glass tells us the water level and whether the water is clean or oily. We test the low-water cutoff, because that is the safety that keeps a steam boiler from firing dry. We look at the pressuretrol setting — most residential steam systems are designed to run at very low pressure, and many buildings we walk into have the control turned up in an attempt to push heat to far units.

From there we check the main vents in the basement, the radiator vents upstairs, the pitch of the mains and runouts, and the return piping. Steam problems almost always live in one of those places, and fixing them is usually far less expensive than the boiler replacement someone may have suggested.

Steam radiator banging and water hammer

Banging is condensate trapped where it should not be. A one-pipe radiator that has settled and now tips away from its valve, a valve left half open, a main that sags between hangers, or a boiler water line set too high will all produce the sharp knock owners know too well. It is loudest on the first cold mornings, when every pipe starts cold.

The repair is mechanical and specific: re-pitching a radiator, correcting a sag, setting the water line, skimming oily boiler water, or replacing a failed main vent. We do not recommend turning the pressure up to quiet a system — it usually makes the noise and the balance worse.

For a longer explanation, read why steam radiators bang or heat unevenly.

Cold radiators and uneven heat between units

Steam can only fill a radiator once the air inside escapes. When main vents are stuck or missing, radiators close to the boiler heat first and the far ones get steam late or not at all. A painted-over or scaled radiator vent does the same thing one room at a time. Balancing a building is a matter of the right vents in the right places, clear mains and a pressure control set where the system was designed to run.

In multi-unit buildings we walk the units during a cycle when we can, note which radiators heat first and which lag, and use that to decide what to replace. That record is also useful to an owner or association when a tenant complaint comes in.

Radiator repair and valve replacement

Cast-iron radiators rarely wear out, but their valves, vents and connections do. We replace leaking radiator valves and packing, swap failed one-pipe vents, repair spud connections, and help with disconnecting and reconnecting radiators for floor refinishing or painting. Two-pipe systems with steam traps need trap testing and rebuilding when one unit overheats or a return line hammers.

When a steam boiler should be replaced

A steam boiler with a cracked section, a leaking firebox or repeated failures of the same safety controls may not be worth repairing. When replacement is the honest answer, the new boiler should be sized to the connected radiation in the building — the radiators actually installed — not copied from the old nameplate, which was often oversized decades ago. Near-boiler piping matters just as much as the boiler itself on a steam replacement.

See boiler replacement and installation for how we size and plan a replacement.

Safety first on steam systems

Turn the boiler off and call if the sight glass is empty, the boiler keeps shutting down on low water, a pipe leaks or sprays, or you smell gas. If you smell gas, leave the building and call the gas utility or 911 from outside before calling us. Every home with a gas boiler should have working carbon monoxide alarms on each level.