Radiator not heating up (boiler): bleeding, balancing and other causes

Radiator not heating up? Usually there is air in the radiator, the boiler’s water pressure is too low or the thermostatic valve is stuck. You can often fix those causes yourself. If some radiators do get warm and others do not, the system may not be balanced properly.

In this article you can read how to find out in a few minutes where the problem is, how to bleed a radiator, check the pressure and free a stuck thermostatic valve. You can also read what hydraulic balancing is and when to call in a professional for radiators and underfloor heating.

Why is my radiator not heating up?

The most common causes are air in the radiator, water pressure that is too low and a thermostatic valve that is stuck. First check whether it is one radiator or all of them, because that tells you a lot about the cause.

• All radiators stay cold: look at the thermostat, the message on the boiler and the water pressure.
• One radiator stays cold: probably air, a stuck thermostatic valve or a closed lockshield valve.
• Cold at the top, warm at the bottom: there is air in the radiator.
• Pipes warm, radiator cold: the valve is not letting water through, for example because the thermostatic valve is stuck.
• Radiators close to the boiler hot, those further away or upstairs lukewarm: pressure too low or a system that is not balanced properly.

A radiator is always a bit cooler at the bottom than at the top. That is normal. Only if the room does not reach temperature is something wrong.

Do you live in Almere and is your home connected to district heating? Then it works differently. In that case, read our article about a radiator that is not heating up with district heating.

How do you bleed a radiator? Step by step

You can bleed a radiator yourself with a radiator key and a cloth. If you hear ticking or a sound like a running stream in the radiator, there is often air in it. This step-by-step plan follows the approach of the Dutch consumer programme Radar:

1. Open all the radiator valves fully.
2. Turn the thermostat up high, for example to 25°C, and let the heating run for 10 minutes.
3. Turn the thermostat down as low as possible and wait another 10 minutes. Then close the radiator valves.
4. Start at the lowest radiator in the house. Hold a cloth under the bleed valve and open it carefully with the radiator key.
5. Close the bleed valve as soon as no more air comes out and water appears. According to Radar, cloudy or black water is not a problem.
6. Repeat this at all the radiators and work your way upwards.
7. Check the water pressure and top up if needed. Then open the radiator valves again and set the thermostat to the temperature you want.

Radar advises bleeding at least once a year. Ideally, do it at the start of the heating season.

Is the boiler’s water pressure too low?

With pressure that is too low, it is mainly the radiators high up in the house that do not get properly warm. The pressure also always drops a little after bleeding, so check the pressure gauge straight afterwards.

The right pressure is in your boiler’s manual. According to Bosch, the ideal water pressure is usually between 1.0 and 2.0 bar, and you add about 0.1 bar per metre of height between the boiler and the highest radiator. How to top up, and when constant topping up points to a leak, is explained in our article on boiler pressure that keeps dropping.

Is the thermostatic valve stuck?

After the summer, a thermostatic valve can get stuck. Under the head there is a small pin that opens and closes the valve. If the valve has been closed for months, that pin can stick. The pipes to the radiator then get warm, but the radiator itself does not.

1. Turn the thermostatic head to the highest setting.
2. Take the head off the valve. Depending on the brand, it is held on with a ring, a clip or a small screw.
3. Gently press the pin in a few times and let it come back up. If it is completely stuck, tap it lightly.
4. Once the pin comes up freely again, put the head back and see whether the radiator gets warm.

Do not force anything. If the valve leaks or something breaks off, close the lockshield valve on the other side and call in a professional. According to the Dutch review platform Werkspot, replacing a faulty radiator valve or thermostatic head costs €40 to €80 including fitting.

Is the lockshield valve closed?

On the other side of the radiator, at the bottom, there is usually a lockshield valve, often under a cap. It controls how much water flows through the radiator. If it was closed after painting or building work, the radiator stays cold.

Do not just open the lockshield valve fully. Its setting has often been chosen deliberately to keep the system in balance. So count the number of turns when you close or open it, so you can always go back to the old setting.

What is hydraulic balancing and when does it help?

With hydraulic balancing (waterzijdig inregelen), each radiator is set so that it gets exactly enough hot water. That helps if the radiators close to the boiler get hot quickly and the radiators further away or upstairs stay lukewarm.

A well-balanced system heats more evenly and uses less energy. A position paper (2025) from organisations including the Dutch sustainable energy association NVDE, the homeowners’ association Vereniging Eigen Huis, the tenants’ union Woonbond and the consumers’ association Consumentenbond states that hydraulic balancing can save up to 20% gas. Balancing takes a calculation per room and adjusting the radiator valves or lockshield valves. If you would like your system balanced, get in touch and we will discuss what we can do for you.

Are the boiler and the thermostat set correctly?

If all the radiators stay cold, first check that the thermostat is set higher than the room temperature and whether the boiler is showing a fault or error code. You can look up an error code in your boiler’s manual.

If the radiators feel lukewarm but the room does get warm, the boiler may be set to a lower flow temperature. Milieu Centraal, the Dutch information centre for energy and the environment, writes that 50 or 60 °C is often enough in a reasonably to well-insulated house. Lukewarm radiators are then not a problem. That is also good to know with a view to the hybrid heat pump from 2029, which works at lower temperatures.

Do it yourself or call in a professional?

You can usually bleed, top up and free a stuck thermostatic valve yourself. If it still does not work after that, or something needs replacing, the work is for a professional.

• Yourself: check the thermostat and the boiler message, bleed the radiators, top up the boiler, free the pin of the thermostatic valve.
• Professional: replace a leaking or broken valve, replace a radiator, balance the system, fix boiler faults and trace leaks.

Do you rent your home? Under the Besluit kleine herstellingen (the Dutch decree on minor repairs), bleeding and topping up are tasks for the tenant. Report repairs to the central heating system to your landlord.

What does it cost to have a cold radiator repaired?

That depends on the cause. A stuck valve is often fixed quickly; a new radiator costs more. Werkspot gives these guide prices (updated 21 August 2026):

• replacing a radiator valve or thermostatic head: €40 to €80 including fitting;
• replacing a radiator: on average €225 to €300 in labour, excluding the radiator itself;
• replacing a radiator including the radiator: on average €250 to €600 per radiator.

Klusbedrijf MSZ works by the hour, without fixed package prices. Send a photo of the radiator, the valve and the pressure gauge via WhatsApp, and we will give you a free estimate.

When should you call a professional?

• The radiator stays cold after bleeding, topping up and freeing the thermostatic valve.
• The valve or the bleed valve is leaking.
• You keep having to top up the boiler.
• The boiler shows a fault that keeps coming back.
• Radiators far from the boiler or upstairs stay lukewarm, while others get hot.

Can you smell gas? Go outside straight away and call the national gas emergency number: 0800 9009.

Frequently asked questions

Why is my radiator cold at the top and warm at the bottom?

Then there is air in the radiator. Air collects at the top, so the hot water does not get there. Bleed the radiator and then check the boiler’s water pressure.

Why does my radiator stay cold while the pipes are warm?

Then the valve is not letting water through. The pin of the thermostatic valve may be stuck after the summer, or the lockshield valve on the other side may be closed.

How often should I bleed my radiators?

Radar advises at least once a year, ideally at the start of the heating season. If you hear ticking or a gurgling sound in a radiator, bleed it in between as well.

Why are the radiators upstairs not heating up?

Often the water pressure is too low. Bosch adds about 0.1 bar per metre of height between the boiler and the highest radiator. If the pressure is fine, the system may not be balanced properly.

What does hydraulic balancing achieve?

Each radiator then gets exactly enough hot water, so the house heats up more evenly. According to a position paper from organisations including NVDE and Vereniging Eigen Huis, it can save up to 20% gas.

As a tenant, do I have to bleed my radiators myself?

Yes. Under the Besluit kleine herstellingen, bleeding and topping up are tasks for the tenant. If a valve is broken or the system leaks, report it to your landlord.

Radiator not heating up? Help in Almere and Lelystad

Is your radiator still not heating up, even after bleeding and topping up? Klusbedrijf MSZ is a family business from Almere and available 24/7. We look at the radiator, the valves and the system, in Almere, Lelystad and the surrounding area. On our page about radiators and underfloor heating you can read what we do. If the problem is with the boiler, see boiler and heating.

The first hour on site costs €181.44 incl. VAT (€149.95 excl. VAT) and is the minimum per visit. After that you pay €108.84 incl. VAT (€89.95 excl. VAT) per hour. In Almere we charge no call-out charge; elsewhere in our service area there is one fixed amount of €42.35 incl. VAT (€35 excl. VAT). For evenings, nights or weekends, we agree the rate with you by phone beforehand. See our prices or ask for a free quote. Call or WhatsApp 06 19 74 36 78 and feel free to send a photo via WhatsApp of the radiator or the pressure gauge.