Bleeding a radiator
In plumbing
Letting trapped air out of a radiator through the small valve at its top corner, using a radiator key, with the heating off and cool. Air makes a radiator cold across the top. On a sealed system, bleeding can lower the pressure, so the gauge is checked once it is done.
Using Bleeding a radiator in a plumbing system
Updated
A distinction worth remembering
Where a radiator is cold points to the fix: air at the top, sludge at the bottom, a valve when it is cold all over, and balancing when only the far rooms lag. Controls then decide when the heat runs and how warm each room gets.
Questions to take further
- Is replacing a boiler notifiable work?
- In England and Wales, yes. An installer registered with a competent person scheme notifies it, or building control is told before work starts. Scotland and Northern Ireland run their own systems, and the gas work goes to a Gas Safe registered engineer.
Sources
- GOV.UK: Approved Document L — Guidance for England on energy efficiency, including heating controls when a boiler is replaced; guidance is not itself the legislation.
- HSE: domestic gas safety FAQs — Gas Safe registration and checking the categories of work on an engineer's ID card.
Where Bleeding a radiator fits in the learning path
The Central Heating section covers these topics:
- Wet Central Heating Systems
- Radiators and Heating Controls
- Heating Pressure and Safe Fault Checks
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- Radiators and Heating ControlsCentral Heating
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A valve on a radiator whose head reacts to the warmth of the surrounding air, shutting down progressively as the room heats up. The numbers on the head are a scale rather than exact degrees. It works best clear of curtains and furniture, and it is normally left off the radiator in the room that has the main room thermostat.
Thermostatic radiator valve
Read the Thermostatic radiator valve entryCompare related terms
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Thermostatic radiator valve — TRV
A valve on a radiator whose head reacts to the warmth of the surrounding air, shutting down progressively as the room heats up. The numbers on the head are a scale rather than exact degrees. It works best clear of curtains and furniture, and it is normally left off the radiator in the room that has the main room thermostat.
Read the Thermostatic radiator valve entrySealed heating system
A heating system with no loft cistern, filled from the mains through a filling loop and kept under pressure. An expansion vessel absorbs the water's expansion as it heats, a gauge shows the pressure, and a relief valve opens if that pressure climbs too high.
Read the Sealed heating system entryMagnetite — Heating sludge
Black iron oxide formed as steel radiators corrode inside a heating system. It settles as sludge along the bottom of radiators and collects in pumps, valves and boilers, causing cold spots, noise and blockages. Cleaning, inhibitor and a magnetic filter keep it under control.
Read the Magnetite entryBefore you start: some plumbing work is regulated or notifiable
Some water fittings work needs notice to, and consent from, the water supplier before it starts. Check the rules where you live.
Gas work is for competent workers covered by a Gas Safe registered business in Great Britain. Northern Ireland has separate gas regulations. Do not work on gas pipes or appliances yourself.
In England, installing an unvented hot-water system over 15 litres is notifiable building work: use a competent installer registered with a competent-person scheme, or tell building control before work starts. Leave this work to a suitably skilled person.
Wales, Scotland and Northern Ireland have their own water and building rules; check which apply before work starts. Electrical connections belong with an electrician.
This guide does not qualify you or make you competent, approved or registered for plumbing, gas or unvented work.
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