Radiator repair: what to know

What the job involves, what changes the price, and what to ask a pro.

What radiator repair is

Radiator repair fixes hot water radiators that stay cold, leak or bang. The work usually means bleeding trapped air, replacing valves and air vents, rebalancing the system, or repairing or replacing damaged radiator sections.

Signs you need it

  • The radiator is cold at the top and warm at the bottom, which usually means trapped air.
  • The radiator bangs or ticks as it heats, or it makes a hissing sound from the valve.
  • Water drips from a valve, a joint or a section where two sections meet.
  • One radiator heats well while the others in the same zone stay cool.
  • The radiator valve is stuck, leaks around the stem or will not turn.
  • The radiator feels rusted, bulging or has a damaged section that looks cracked.

What the pro does

  • Check the boiler pressure and confirm the system is cool before opening any valve.
  • Bleed the radiator at its air vent, then check whether the top of the radiator heats evenly.
  • Test the supply and return valves, and replace the valve packing or the thermostatic head if they leak or stick.
  • Replace damaged sections, nipples or gaskets, and check the joints for leaks under pressure.
  • Rebalance the system by setting the valves in each room so the water reaches every radiator.
  • Run the heat up, check each radiator again, and confirm there are no leaks at the joints.

What changes the price

Every job is different, so we do not publish prices. These are the things that move the quote up or down.

  • Whether the job is a single radiator or a whole system, since each radiator adds time.
  • Radiator type, such as cast iron sectional, panel or baseboard, which changes the parts needed.
  • Whether a valve, vent or section must be replaced, or only bled and tightened.
  • Access to the radiator and its piping, such as under a window or behind furniture.
  • Condition of the joints and nipples, which can need cutting, rethreading or replacing.
  • Whether the whole system needs rebalancing or only one radiator needs attention.

What a written quote should spell out

  • Each radiator listed by room, with the fault found in it.
  • Each part replaced, such as a valve, a vent, a section or a gasket, with its size or model.
  • The rebalancing work, listed as a separate item.
  • Whether the pressure of the boiler was checked and adjusted, and to what level.
  • Warranty terms on the parts and the labor.

Questions to ask before you hire

  • Did you find out why the radiator is cold, or only bleed it?
  • Will you check the valve packing and the thermostatic head, and replace them if they leak?
  • Can you match the replacement section to my existing radiator?
  • Will you rebalance the system so the far radiators get heat?
  • Will you check the boiler pressure before and after the work?
  • Do you test the joints under pressure before you leave?
  • Will you tell me which radiators need attention now and which can wait?

Red flags

  • The pro bleeds every radiator and says the work is done without checking the valves or the rebalancing.
  • The pro replaces a whole radiator when a valve or a section is the actual fault.
  • The pro cannot match the replacement section to the existing radiator.
  • The pro will not show the joints tested under pressure.

What you can do yourself

With the system cool, you can bleed a single radiator with a radiator key, and you can tighten a loose packing nut on a valve if it is only a little loose. Do not open the boiler, its pressure relief valve or the main system valves, and do not try to cut or weld a leaking pipe. Valve replacement, section replacement, joint repair and system rebalancing belong to a licensed heating technician.

Licenses and permits

Radiator repair is commonly done by licensed plumbing or heating contractors, and piping or gas work may need a separate license. Check with your state or local licensing agency for the requirements that apply to your repair.

Radiator repair questions

Why is my radiator cold at the top?

Trapped air is the usual cause. Bleed the radiator with the system cool. If it stays cold, the valve may be closed, the system may be unbalanced, or water may not be flowing through it.

Why does my radiator make banging noises?

Banging often comes from trapped air, water moving through a radiator that is not pitched level, or a valve that closes too fast. A technician can check the air and the valves together.

Can a cast iron section be replaced?

Often yes. A damaged section can be replaced if a matching section is available, and the joints are sound. Ask the technician to match the section size and check the nipples before the work.

Should I replace the radiator valves?

Replace them if they leak around the stem, will not turn or do not shut off the flow. Valves that work and do not leak can stay.

About this guide

This national guide is written and checked by infinibell. Rules and conditions differ by place, so local pros are credited on guides for the cities they serve, not on national ones.

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