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When do radiators need bleeding?
Air in a heating system always rises to the highest point – the top of the radiator. There it pushes out the hot water, and the radiator no longer heats properly. Bleed it when you notice any of these signs:
- The radiator is warm at the bottom and cold at the top
- You hear gurgling, trickling or rushing inside it
- The room won’t warm up even with the thermostat turned fully up
- At the start of the heating season, after months switched off
- After work on the heating system or after the system was topped up
What tools do I need?
You only need three things. A radiator key (Entlüftungsschlüssel) costs very little at any DIY store and fits the square valve at the top side of the radiator. Some newer valves take a flat screwdriver instead.
- Radiator key (or a screwdriver, depending on the valve)
- A cloth or old towel
- A small container, such as a mug or cup
How to bleed a radiator in 7 steps
If you have several radiators, start with the one closest to the boiler and work your way outwards and upwards.
- 1. Turn the heating on, set the thermostat to maximum and let the radiator get warm.
- 2. If your flat has its own gas boiler, switch the boiler or circulation pump off and wait half an hour to an hour so the air collects at the top. With central heating, skip this step.
- 3. Put the cloth under the bleed valve and hold the container beneath it.
- 4. Fit the key and turn it slowly anticlockwise – half a turn is enough. Never unscrew the valve completely.
- 5. The air escapes with a hiss. Wait until only water comes out, with no bubbles.
- 6. Close the valve clockwise – hand-tight, no force.
- 7. Switch the heating back on, check the water pressure and set the thermostat back to normal.
Gas boiler or central heating – what’s different in Berlin?
Many Berlin Altbau flats have their own gas boiler on the kitchen or bathroom wall – known as Gasetagenheizung. It heats only your flat. Bleeding lets a little water out of the circuit, so the pressure drops. Check it on the boiler’s pressure gauge or display.
For many wall-mounted boilers the recommended pressure is roughly 1 to 2 bar; some models and larger systems need more. What counts is the value in your boiler’s manual or the marking on the gauge. If pressure falls too low, many boilers shut down and show an error code. The manual also explains where the filling valve is and how to top up – if in doubt, ask a heating professional.
In buildings with central heating – prefab Plattenbau blocks, new builds and many renovated older buildings – every flat is connected to one system in the basement. Tenants don’t manage its pressure; the property manager (Hausverwaltung) or caretaker does. Bleed your own radiators as described, and tell the Hausverwaltung if several radiators stay cold afterwards.
| Own gas boiler (Gasetagenheizung) | Central heating | |
|---|---|---|
| Where is the heating? | Boiler in the flat, often kitchen or bathroom | Shared system in the basement |
| Switch off before bleeding? | Yes, recommended | Not possible, not needed |
| Who checks the pressure? | You, on the boiler’s gauge | Property manager or caretaker |
| Topping up water | Following the manufacturer’s manual | Not yourself |
What should I watch out for?
Heating water can be hot – keep your hands and face away from the valve and turn slowly. The water is often dark and stains carpets and wooden floors, hence the cloth. Never open the gas boiler’s casing.
If you smell gas, don’t touch light switches or doorbells, open the windows, leave the flat and call your gas supplier’s emergency service or 112 from outside.
When should you call a plumber?
Bleeding fixes most cold radiators. Call a professional if any of these apply:
- The radiator keeps going cold after bleeding, or you have to top up constantly
- The bleed valve is stuck or won’t close properly
- Water is leaking from the valve, a fitting or the radiator itself
- The thermostat head is broken or the valve pin underneath is stuck
- One radiator stays cold while all the others heat up
What we do – and what we don’t
Our staff replace thermostat heads and valves, fix leaking fittings and find out why a radiator stays cold. Work on the gas boiler itself we pass on to a specialist company licensed for it. In rented flats the landlord usually arranges boiler servicing, so report boiler faults to your Hausverwaltung first.