How to Balance Your Radiators

When some radiators heat much faster than others — leaving some rooms too hot and others too cold — the system is unbalanced. Balancing adjusts the flow of water to each radiator so they all reach temperature at roughly the same time.

What you need

• Lockshield valve key (or a small adjustable spanner)
• Clip-on pipe thermometer or infrared thermometer
• Patience — this process takes 1–2 hours

How central heating flow works

The pump pushes water around the circuit. Radiators closest to the boiler receive water first and tend to heat faster. Radiators furthest away heat more slowly. Balancing restricts flow to the nearest radiators, allowing more flow to the furthest ones.

Step-by-step balancing

1. Turn the heating off and let the system cool completely.
2. Open all radiator lockshield valves fully (remove the cap, turn anti-clockwise until fully open).
3. Turn the heating on at full temperature.
4. Note which radiators heat up first — these are "nearest" the boiler in circuit terms.
5. On the radiators that heat fastest, slowly restrict the lockshield valve by turning clockwise. A quarter-turn at a time. Aim for the flow-to-return temperature difference (measured at the pipe entering and leaving the radiator) to be approximately 10–12°C. A faster-heating radiator will have a larger temperature difference — reduce the lockshield until the difference is approximately 10°C.
6. Work through all radiators, adjusting as you go, until all are heating at a similar rate.

When to call an engineer

If balancing doesn't resolve the issue, you may have a pump problem, a partly blocked radiator, or a system design issue. Book a diagnostic visit.