Boiler Not Heating
Boiler running but no heat, or boiler won't fire? Common causes in steam and hot-water systems and when to call a licensed boiler technician.
Boiler Repair services
Each guide below covers one specific winter problem: symptoms, causes, what you can safely check and what a licensed technician does. Prices are explained in the boiler repair cost guide.
Boiler Pressure Problems
Boiler pressure dropping, climbing above 25 PSI or relief valve dripping? What normal pressure is and how expansion tanks and fill valves cause problems.
Leaking Boiler Repair
Water under the boiler? Relief valve, pump seal, fittings or a cracked heat exchanger. How to tell where a boiler leak comes from and what to do.
Steam Boiler Repair
Steam heat banging, radiators cold or boiler shutting off on low water? Steam boiler repair explained by system part, for older US homes and buildings.
Radiator & Baseboard Not Heating
One radiator cold, cold at the top, or baseboard heat not working in one room? Bleeding, balancing, zone valves and when to call a technician.
Common winter problems and where to start
| Problem | What usually causes it |
|---|---|
| Boiler running but radiators cold | Air, a failed circulator or a zone valve. Boiler no-heat guide. |
| Pressure gauge too high or too low | Expansion tank, fill valve or leak. Pressure problems. |
| Water under the boiler | Relief valve, pump seal or a cracked section. Leak diagnosis. |
| Steam pipes banging | Water hammer from pitch or water-level problems. Steam boiler repair. |
| Some radiators cold, others hot | Air, balancing or a stuck vent. Radiator repair. |
Watch: winter heating explained
Short, silent clips hosted on muse.ai that show what to look for. They play muted and loop.
Coverage map: all 50 states and DC
Pick your state for local winter conditions, common heating fuels and the cities we route calls from. Colors show how severe winters are, based on IECC climate zones.
- Severe cold (IECC 6–8)
- Cold (5)
- Mixed (4)
- Mild (1–3)
How it works
- Tell us whether it's steam or hot water, the fuel, and what you see on the gauge.
- We connect you with a licensed hydronic provider covering your area.
- The technician checks firing, pressure, water level, circulation and venting.
- You approve the price before work begins.
- Every zone or radiator is checked for heat before the job is closed.
Decision guide
| Clue | Steam system | Hot-water (hydronic) system |
|---|---|---|
| Gauge | Reads in ounces or a few PSI | Reads about 12–25 PSI in normal operation |
| Radiators | Air vent on the side, one pipe or two | Bleed screw at the top; baseboard fin-tube common |
| Sight glass | Yes, shows the water level | No |
| Common issue | Banging pipes, low water cutoff | Air in the lines, circulator, pressure |
| Guide | Steam repair | Pressure · Radiators |
Before you call
Have the equipment type, brand and any blinking error code ready, and note what you've already checked. If anyone at home smells gas or a CO alarm sounds, leave the house and call 911 or the gas utility first.
Brassline Boiler Repair is a referral service. Your call is connected to an independent, licensed provider who serves your ZIP code and quotes the job directly. How it works.
Boiler Repair questions, answered
What pressure should my boiler be at?
Most residential hot-water boilers run around 12–15 PSI cold and up to about 20–25 PSI hot. The relief valve is usually set to 30 PSI. Steam boilers run at very low pressure, often under 2 PSI. Check your boiler's manual for exact figures.
Why is my boiler pressure relief valve dripping?
Usually because system pressure is reaching about 30 PSI. A waterlogged expansion tank or a leaking fill valve is the common cause. Don't cap the valve; have the cause fixed.
How do I know if I have a steam or hot-water boiler?
Steam boilers have a sight glass showing the water level and a low-pressure gauge. Hot-water boilers have a combination pressure/temperature gauge, an expansion tank and a circulator pump.
Why are my radiators cold at the top?
On hot-water systems, trapped air collects at the top. Bleeding the radiator usually fixes it. If it keeps happening, the system may be drawing in air or the fill valve isn't maintaining pressure.
Why does my steam heat bang?
Water hammer happens when steam meets pooled condensate, usually because a pipe or radiator lost its pitch, the boiler water level is too high, or a vent is stuck.
How long do boilers last?
Cast-iron boilers often last 20–30 years or more with good maintenance; high-efficiency condensing boilers commonly run 15–20 years. Water quality and annual service make a big difference.