Balance your radiators so heat spreads evenly across the house, using a thermometer and the lockshield valve on each one.
RB-01Understand what balancing doesBalancing adjusts how much hot water flows through each radiator, so ones close to the boiler don't hog the heat and starve rooms further away. You do it by measuring the temperature drop across each radiator and closing the lockshield valve (the one under the plastic cap, without a dial) to slow flow where needed. It takes 30-60 minutes for a typical house with 8-10 radiators.
RB-02Gather your toolsYou need a radiator key to open bleed valves, and something to measure temperature — an infrared thermometer gun is easiest, or two ordinary thermometers taped to the pipes. Grab a small cloth for any drips and a notepad to write down settings as you go.
RB-03Bleed every radiator firstAir trapped in a radiator gives a false temperature reading, so bleed all of them before you start balancing. With the heating on, hold the key on each bleed valve, turn slowly until water hisses or dribbles out, then close it. Have your cloth ready and check the boiler pressure afterwards — top it up if it's dropped below 1 bar.
RB-04Open every valve fullyTurn every thermostatic radiator valve (TRV) to its highest setting and make sure every lockshield valve is fully open too. This gets maximum flow through the whole system so you're starting from a level playing field. Leave the heating running for 15-20 minutes so every radiator gets properly hot.
RB-05Find the radiator nearest the boilerWork out which radiator is closest to the boiler on the pipework — usually it's in the same room or nearby. You always balance starting here and work outward, because it sets the reference for every other radiator.
RB-06Balance the first radiatorWith the radiator hot, measure the temperature of the pipe going in (flow) and the pipe coming out (return) at the valves. You want the return about 10-12°C cooler than the flow. If the difference is smaller, close the lockshield slightly with a small spanner or the radiator key; wait a few minutes and measure again.
RB-07Work outward through the rest of the houseMove to the next nearest radiator to the boiler and repeat the same measurement and adjustment. Keep going room by room, always moving further from the boiler, until you've balanced every radiator in the house. Write down each setting so you don't lose track of which ones you've done.
RB-08Recheck the whole systemOnce every radiator is balanced, let the system run for another 15 minutes, then walk round and feel each one. They should all be evenly hot from top to bottom, with the far radiators heating up almost as well as the ones near the boiler. Nudge any lockshield that's still not quite right and recheck.
RB-09Turn TRVs back to normal and tidy upSet each thermostatic valve back to your usual comfort setting for that room rather than leaving them on maximum. Wipe up any drips, put the tools away, and keep your notepad of lockshield settings somewhere handy in case you ever need to redo this after work on the heating system.
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