Bleeding a Radiator in Germany (Heizung entlüften): Tips, Responsibilities, and Step-by-Step Guide
A gurgling radiator or a heater that’s only half warm usually means there’s air trapped inside the radiator. That doesn’t just reduce comfort—it can also increase heating costs because your system needs more energy to deliver the same warmth.
The fix is simple: bleeding the radiator (in German: Heizung entlüften). With a few basic tools and a couple of minutes per radiator, you can remove trapped air so the system heats more evenly and efficiently.
This guide explains:
- why bleeding matters,
- how to do it safely step by step,
- what to do after bleeding (pressure check),
- and who is responsible in German rental properties.
Why Bleeding a Radiator Matters
Air in the heating circuit stops hot water from circulating properly. Typical symptoms include:
- gurgling / bubbling / tapping sounds
- radiator cold at the top but warm at the bottom
- rooms taking longer to heat (or never reaching the set temperature)
When the radiator can’t heat properly, people often turn the thermostat up—leading to higher energy use with less comfort.
Best practice: bleed radiators once per year, ideally before the heating season starts (often in autumn), and whenever you notice the symptoms above.
Step-by-Step: How to Bleed a Radiator (Heizung entlüften)
What you’ll need
- a radiator bleed key (small square key, cheap at hardware stores)
- a small cup/bowl to catch water
- a cloth/towel (and optionally gloves)
1) Turn heating off and let things settle
- If you control the system: turn off the heating (and circulation pump if accessible).
- In an apartment where you can’t access the boiler: turn your heating down/off and wait a bit.
Wait 30–60 minutes so air can collect at the top of the radiators.
2) Open the thermostatic valve fully
Set the radiator thermostat to its highest setting so the valve is open.
3) Place the cup and cloth under the bleed valve
The bleed valve is usually at the top side of the radiator (opposite the thermostat).
4) Open the bleed valve slowly
Insert the key and turn slowly (usually about a quarter turn).
You should hear a hissing sound as air escapes.
5) Close the valve when water flows steadily
Keep the valve open until:
- the hissing stops, and
- water comes out in a steady stream (without air spurts)
Then close the valve gently—hand tight, not over-tight.
6) Check heating performance
Turn the heating back on and confirm the radiator warms up evenly and the noise disappears.
Tip: Bleed radiators starting with the lowest floor (or the radiator closest to the boiler) if you’re in a house you control—then work upward. In apartments, just bleed the radiators that show symptoms.
After Bleeding: Check System Pressure (Important)
Bleeding releases a bit of water, which can reduce system pressure.
If you have your own boiler (e.g., a single-family home)
Check the pressure gauge. Many boiler manufacturers recommend roughly:
- around 1.0–1.5 bar when the system is cold
- around 1.0–2.0 bar when heating is running
If pressure is low, topping up may be necessary—always follow your boiler manual.
If you live in a rental with a central boiler (very common in Germany)
Tenants often should not top up the central system themselves. If pressure is low or radiators stay cold after bleeding, notify the landlord / property manager / caretaker.
Rentals in Germany: Who Is Responsible?
Landlord’s duty: working heating
In Germany, landlords must ensure the heating system works properly and can achieve reasonable indoor temperatures during the heating period (often cited around 20–22°C daytime and lower at night, depending on circumstances).
Tenant’s role: simple measures are often allowed
Bleeding a radiator is considered a simple, low-risk action. Many landlords and managers expect tenants can do it—but tenants are generally better protected when they report the issue, especially if:
- they don’t have the right tool,
- the valve is stuck,
- they’re worried about leaks,
- multiple apartments are affected (system-level air/pressure issue).
Practical rule:
- Tenants: report early, bleed if comfortable.
- Landlords/managers: provide guidance, tools (or caretaker support), and handle any system pressure or technical faults.
Troubleshooting: Radiator Still Cold After Bleeding
If bleeding didn’t fix it, common causes include:
- Low system pressure (especially after bleeding many radiators)
- a stuck thermostat pin/valve
- sludge/build-up in the radiator
- hydraulic imbalance (system needs balancing)
- boiler/circulation pump issues
If you’re a tenant: document the problem (photo/video + room temperature) and notify your landlord/property manager.
FAQ: Bleeding Radiators (Heizung entlüften)
How often should radiators be bled?
Usually once per year before the heating season—and any time you hear gurgling or notice uneven heating.
How do I know if there’s air in my radiator?
Gurgling/bubbling sounds and a radiator that’s cold at the top are classic signs.
Who must bleed radiators in a rental apartment—tenant or landlord?
Landlords are responsible for a functioning heating system. Tenants are often allowed to bleed radiators, but if they can’t or don’t want to, they should report it and the landlord/manager should arrange help.
What if I don’t have a bleed key?
Buy one (it’s inexpensive), ask the caretaker/manager, or borrow one from a neighbor. Avoid forcing the valve with unsuitable tools.
Radiator still cold after bleeding—what now?
Check system pressure (if you control it) and make sure the thermostat valve isn’t stuck. If the issue persists, contact your landlord/manager—there may be a system-level problem.