Boilers are reliable workhorses, most Pittsburgh-area boilers run 20-30 years with proper care. But like any mechanical system, problems show up over time. Here’s a guide to the most common boiler issues we see across the Pittsburgh metro, what causes them, and what you can fix yourself vs what needs a licensed boiler tech.
Most common cause: Failed thermocouple (older gas boilers), dead aquastat, low water pressure, or air trapped in the lines.
Quick check:
Call a pro if: Pressure rises but heat doesn’t return, or you can’t get the boiler to fire. Most no-heat calls in Pittsburgh come down to thermocouples, aquastats, zone valves, or circulators, all parts our service trucks carry for same-day repair.
Most common causes: Pressure relief valve discharging, waterlogged expansion tank, pinhole in copper supply line, gasket failure on a circulator or zone valve, or, worst case, a cracked heat exchanger.
Where is the water?
Call a pro: Anything beyond turning off the system and putting a bucket under the drip. Boiler water repairs require draining and pressurizing, not DIY territory.
Banging on startup: Water hammer from trapped air. Bleed radiators systematically (top floor first, working down).
Kettling (rumbling like a tea kettle): Scale buildup on the heat exchanger trapping water that boils unevenly. Needs descaling or, in severe cases, heat exchanger replacement.
Whistling: Usually a failing circulator pump bearing or a partially closed zone valve. Replace the pump or open the valve fully.
This is a safety issue. A gas boiler should burn with a clean blue flame. Yellow indicates incomplete combustion, which produces carbon monoxide. Causes include dirty burners, blocked flue, gas pressure issues, or wrong fuel mix.
What to do right now: Shut the boiler off. Make sure CO detectors are working. Call us at (412) 376-9080. Do not run the boiler until a tech has done combustion analysis and verified safe operation.
Normal cold pressure: 12-15 PSI for most residential boilers.
Normal hot pressure: 18-25 PSI.
Pressure too low (below 12 PSI cold): System has lost water. Could be a slow leak, recent bleeding, or a failed auto-fill valve. Open the auto-fill manually to bring pressure back to 15 PSI cold.
Pressure too high (above 30 PSI): Expansion tank failed (waterlogged), auto-fill valve stuck open, or backflow preventer failed. The relief valve will discharge to protect the boiler, don’t block it. Replace the expansion tank.
Most common cause is a failed thermocouple. The thermocouple senses pilot flame and tells the gas valve it’s safe to open. When the thermocouple fails, the gas valve closes and the pilot goes out. Thermocouple replacement is a same-day repair, typically $200-$400.
If the thermocouple is new and the pilot still won’t stay lit, suspect: weak gas pressure, draft pulling the pilot out, partially blocked pilot orifice, or a failing gas valve.
Common causes:
Air trapped in the radiator. Use a radiator key to open the bleed valve at the top of the radiator until water comes out, then close. Do top-floor radiators first; the air rises through the system.
If bleeding doesn’t work, you may have stuck zone valves or a failing circulator.
Anything involving:
Hoffner Heating & Air Conditioning offers 24-hour emergency boiler repair across the Pittsburgh metro, Pitcairn, Monroeville, Murrysville, Penn Hills, Wilkinsburg, Plum, and beyond. Call (412) 376-9080 or learn more about our Pittsburgh boiler repair services.