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Bleeding radiators and checking heating pressure: what you can do yourself
Short answer: turn the heating off, let everything cool and bleed radiators from low to high until water comes. Then check the pressure of the system. If pressure keeps falling or you must top up often, there is more going on than air. This blog is only about bleeding and looking; topping up and repairs to an appliance follow the appliance directions or belong to an installer.
👷 Calling in a professional is never unnecessary. A certified installer is needed for an appliance that stays in fault, pressure that falls quickly, a leak, gas or work on the heating system. For gas, a certified installer is the only correct route.
What matters most
- Air sits at the top: a radiator that stays cold at the top and gurgles often points to air. A radiator that stays cold at the bottom can have another cause.
- Order helps: start low and end at the highest point. Keep an 12-litre bucket and a cloth at the valve.
- Pressure is a signal, not a goal: read the gauge when the system is cold. Note the reading and look again after a day. A loose thermostat or room control does not replace checking the system itself.
What do you need?
- A bleed key and a cloth, plus a construction bucket in case more water comes than expected.
- A rechargeable LED work lamp if valve or gauge is in a dark cupboard or corner.
- A water pump pliers set, an adjustable wrench and a pipe wrench only to refit a cap hand-tight, never to force a valve. A multifunction wall detector, a tape measure with auto-lock and a carpenter pencil only help mark places for an installer, not to open pipes yourself.
How to do it
- Turn the heating off and wait until radiators and pipes have cooled.
- Start at the lowest radiator, open the valve a little and close it as soon as a calm stream of water comes.
- Work upwards and check each radiator for a warm top after restarting.
- Read the pressure and note it. If the appliance directions say to top up, follow only those directions or call an installer.
- Check again after a day. If pressure falls again, you see moisture or a radiator stays cold, have an installer investigate. Also read our blog on getting your home ready for winter about making the home ready for winter.
Working safely
Wear work gloves with nitrile coating against dirty water and safety goggles if a valve can spray. Never open a hot radiator and do not force a stuck valve with large tools. For gas, a smell of fumes or an appliance fault, stop and call a certified installer.
Why does only the top stay cold?
Air collects there. Bleeding often helps then. If the bottom stays cold or the whole radiator, flow or control can be the cause.
How often is topping up normal?
A little now and then after bleeding can happen. Frequent topping up or quickly falling pressure is a sign to have an installer look for a leak or faulty part.
You can bleed calmly yourself. As soon as pressure, leakage or the appliance itself comes into view, the installer is the next step.
Read also: How to paint a radiator and How to insulate an attic
Where can you find everything for this job?
At Saniso, the online store for DIYers and professionals, you will find tools, materials and personal protective equipment for your job.
- Browse our construction tools and our workwear and safety.
- Create a customer account and order easily.
- Working on a bigger project or want to hand over the job? Request a project quote.
- Book a showroom visit, at least 24 hours in advance.
- Not sure which material suits your job? Get in touch with us.
In doubt about the approach? Feel free to call in a professional.
Saniso – Build your home with Saniso.
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