How long do radiators last, and when should you replace one?

Typical lifespan by radiator type

There is no fixed expiry date. The figures below are rough expectations for a radiator on a system that is looked after. A radiator on a system full of sludge can fail in a fraction of that time, and one on a system that has been cleaned and dosed with inhibitor can easily outlast them.

What shortens a radiator's life

Steel radiators rust from the inside when oxygen gets into the heating water. The rust forms black sludge, known as magnetite, which settles in the bottom of the radiators and in the boiler. Over time the steel thins until a pinhole opens, usually along the bottom edge or a welded seam.

Anything that brings fresh water into the system speeds this up. A system that loses pressure and gets topped up every few weeks is constantly taking in new oxygen. So is an open-vented system with a feed and expansion tank that pumps over or draws in air. A central heating inhibitor slows the corrosion, and a magnetic filter catches the sludge before it reaches the boiler, which is why both matter for the radiators as well as the boiler.

Outside damage matters too. Radiators in bathrooms and kitchens, or over wet floors, can rust from the outside. Paint that has been chipped or damaged by cleaning products lets moisture reach the steel.

Signs a radiator is reaching the end

Some symptoms mean the radiator itself is failing. Others look worrying but are about the valves or the system, and a new radiator will not fix them.

• Water weeping from the panel, a seam or a pinhole, often with a brown stain or crust on the bottom edge
• Rust showing through the paint, especially along the bottom or on the back
• Staying cold at the bottom after the system has been flushed, suggesting the radiator is packed with sludge
• Heating more slowly than the others in the house even when balanced
• Physical damage: dents, cracks, or a bracket pulling away from a weakened wall fixing

A radiator that is weeping from the body cannot be reliably repaired. Sealants added to the system are, at best, a short-term measure and can cause problems elsewhere. Put a container under it, turn both valves off if you can, and arrange a replacement.

Repair or replace?

Most radiator problems are repairable, and it is worth ruling those out before paying for a new one. The table sets out the usual answer.

Should you replace radiators with a new boiler?

Not automatically. Sound radiators can stay in place when the boiler is replaced, as long as the system is cleaned first. The Domestic Building Services Compliance Guide expects the heating system to be flushed and cleaned when a new boiler goes in, and an inhibitor added, so that sludge from the old radiators does not damage the new boiler.

Replacement makes more sense where radiators are already corroded, where some rooms never get warm enough, or where you want to run the system at a lower flow temperature for efficiency. A lower flow temperature means each radiator gives out less heat, so undersized radiators may need upgrading. Our guide to choosing radiator size and output explains how to check each room. If you are thinking about a heat pump in future, radiator sizes will be part of that design, and it is worth planning for it now.

What replacing a radiator involves

A like-for-like swap, where the new radiator has the same pipe centres and the pipes stay where they are, is a relatively quick job. The radiator is isolated or the system drained down, the old one removed, the new one hung and connected, then the system refilled, bled and dosed with inhibitor. New valves are often fitted at the same time, because old valves that have not been moved for years may not seal or turn.

It becomes a bigger job when the new radiator is a different size, when the pipes come up through a solid floor, or when the radiator is fed by old microbore pipes that are partly blocked. Cast iron radiators need extra planning because of their weight and the wall fixings. Our guide to cast iron radiator replacement planning covers those.

Book a radiator check or replacement

Loyal Plumbers carries out radiator repair and replacement across London and everywhere inside the M25, from single leaking radiators to replacing every radiator on a system. We also clean systems with power flushing where sludge is the real problem, and handle wider central heating repairs.

Call us or send an enquiry with photos of the radiator, where it is leaking or which part stays cold, how old the system is and whether it has been flushed. We will tell you whether a repair, a clean or a new radiator is the right answer.