What to do if the radiator gurgles and whistles?

Gurgling, hissing, whistling: noises from the radiator are not only annoying. They also indicate that there is too much air in the heater and it is no longer efficiently dissipating heat. Then the only thing that often helps is to bleed the heater. But caution is advised here: “Uncontrolled ventilation is a problem,” warns Matthias Wagnitz from the Central Association for Sanitary, Heating and Air Conditioning (ZVSHK). Frequent venting can even exacerbate the problems, says the consultant for energy and heating technology.

However, correct ventilation also saves heating costs. “Only a ventilated radiator works properly, heats up optimally,” says Martin Steinestel, energy officer at the NRW consumer advice center.

But how do you know if you should bleed your heating? Why is your radiator still not getting warm? What do the noises mean exactly? What can you do yourself and when do you need help from a craftsman? The most important questions and answers about venting the heating system correctly.

When and why should I bleed my heater?

If your heater is making a gurgling sound, it usually has too much air in it and it’s a good idea to bleed it. The disturbing noises arise because the heating water no longer flows completely through the radiator due to the air cushion.

A heater heats the room via the heating water. Air in the radiator acts as insulation and prevents heat from being emitted. As a result, more hot water has to flow through the radiator to maintain the room temperature. So the heating is less efficient.

With a quiet, functioning heater, there is no need for action: “As long as I don’t hear any gurgling noises, I don’t have to bleed the heater,” says expert Matthias Wagnitz.

How much does it save to vent the heater?

“Of course, a well-vented heating system has a saving effect,” says Martin Steinestel from the consumer center. Because then the radiator can be used better and the heating system can be adjusted more efficiently. However, an exact calculation of how many euros consumers can actually save is difficult and depends on many factors.

Can you bleed a heater yourself?

With a little prior knowledge, you can bleed your heating system yourself. For venting you will need

• a bleed key,
• a rag
• and a bowl to catch any excess water.

You can get a suitable venting key from any hardware store.

Bleeding the heating without a key – a good idea?

No, you shouldn’t open the radiator’s bleed valve without a bleed key. A pipe wrench is not an alternative: “For God’s sake, no, please don’t use pliers!” warns Matthias Wagnitz from the ZVSHK. They could damage the heater.

Where do you start to bleed the heater?

If there are several radiators in the house, it is advisable to work your way up from the bottom, possibly in several passes. In the apartment, the order is not important.

Before venting, homeowners should ensure that the heating system has the optimum overpressure, emphasizes consumer advocate Steinestel. This is the only way to squeeze out the air bubbles when venting. If the pressure is too low, the heating system must be topped up with heating water. As a tenant, it is best to find out from your landlord or the property management company about the current status of the heating.

Step-by-step instructions: Bleed the heater

1. As the owner, turn off the circulation pump before venting. This interrupts the flow of water in the heater. Then the air bubbles can collect in the radiators and escape more easily when venting. As a tenant, you can also vent without switching off the pump.
2. Set your heating thermostat to the highest level.
3. Hold a rag or, if possible, a container to the vent valve. Escaping heating water is caught in this way. You can find it at the end of the radiator without a temperature controller.
4. Now carefully open the valve with the vent key. A quarter to half a turn is enough. The escaping air makes a hissing sound and water comes out of the valve. Catch the occasionally hot water in the bowl.
5. Close the valve again as soon as the hissing stops. So you don’t lose water unnecessarily. The radiator is now vented.
6. Turn on the circulation pump again if it was previously turned off.

Should I top up with water after bleeding?

Venting reduces the pressure in the heating circuit. You should therefore check the pressure if you bleed the system frequently and top up the heating water if necessary. This is often necessary if the heater is not serviced regularly.

In extreme cases, a vacuum is created without refilling, which causes the heater to suck in air when venting. “Then at some point I no longer bleed the heating, but ventilate it,” explains Matthias Wagnitz. In addition, the oxygen in the heating pipes causes corrosion.

If you bleed many or even all radiators, then the heating water should definitely be topped up, recommends the ZVSHK engineer.

Without experience, however, you should leave the refilling to a person from the field. Contaminated water damages the heater and air in the hose can quickly get back into the system. In addition, refilled water may need to be desalinated or softened. “Once you’ve talked about it in detail with your craftsman, you can do it yourself,” says Wagnitz.

Bleeding the heating: What should be considered in the rented apartment?

In the event of disturbing noises or other problems with your heating, you should first contact the landlady or the property manager. The same applies to apartment owners in a community facility. “If the landlord doesn’t find out about the problems, he can’t fix anything,” says Matthias Wagnitz.

Contacting them is particularly important to find out when the heater was last serviced and whether the pressure is optimal. After venting, you should also let them know that the water in the heating system should be refilled.

As a tenant, you have the right to receive instruction on how to use your heating system. “Owners and landlords have a special responsibility to operate their technology properly and energy-efficiently. Accordingly, the maintenance and measures to optimize a heating system must also be documented in a comprehensible manner,” says Martin Steinestel from the consumer advice center.

Heating keeps making noises: what to do?

You should be able to fix a gurgling sound by venting. If the heating still whistles or hisses afterwards, a hydraulic adjustment by a tradesman may be necessary. Another reason for noise in the heater could be that the circulation pump is not set correctly.

If the heater knocks or cracks, the heater pipes are often attached too tightly. Radiators and pipes can then not expand when heated without noise. As long as the noise is not very distressing, you can ignore it.

Why doesn’t the heater get warm despite venting?

If the heater does not warm up properly despite venting, a hydraulic adjustment may also be necessary. “Hydraulic balancing ensures that every radiator in the house receives exactly the amount of water it needs,” explains Matthias Wagnitz from the ZVSHK. Because especially with old heating systems, water can hardly reach the radiators that are far away.

For a hydraulic balance, craftsmen calculate the specific settings, for example for the heating load, water volume and pressure in the pump, and then completely reset the heating system. The valves usually have to be replaced. By balancing, you can increase the efficiency of the heating system and reduce your heating costs in the long term.

A stuck heating valve or a broken thermostat can also ensure that the heating no longer heats up. Even then, the help of a craftsman is recommended.

Heat pump installation: how important is hydraulic balancing?

Careful venting of a heating system, but also hydraulic balancing, ensure that the heating system runs more efficiently. This is particularly interesting if you want to install a heat pump.

For the installation of a heat pump, the flow temperature in the boiler should be as low as possible. Because the efficiency of a heat pump depends on the temperature difference between the heating and the outside temperature. The lower the flow temperature, the more worthwhile a heat pump is from a financial point of view. With good heat pumps, the flow temperature in the boiler can be up to 60 degrees on the coldest day of the year, explains Matthias Wagnitz from the ZVSHK. Less is always advantageous.

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