Preparing your central heating boiler for winter: what to check before the season starts

During the summer, your heating boiler typically only heats water. Meanwhile, the radiators and the entire heating circuit remain idle for months. Therefore, when the first cold snap arrives, many people encounter the same problem: hot water is available, but the radiators won't heat up, the boiler displays an error, or the radiators are only lukewarm. During this time, demand for technicians is at its peak, and you often have to wait several days.

That is why it is best to check your heating system before the season begins, ideally by mid-October, before you truly need it. In this article, we will explain what you can do yourself and when it is better to call a technician.

1. Check the system pressure

There is a manometer (a pressure gauge needle or digital display) on the boiler. In a cold system, the pressure should typically be between 1–1.5 bar. The exact standard is specified in your boiler's manual.

• If the pressure is below 1 bar, the system lacks water. Most boilers have a special valve for this. If you do not know where it is or how it works, it is better to leave it to a technician.
• If the pressure drops frequently, there is a leak somewhere: in a pipe, a radiator connection, or the boiler itself. In such cases, adding water is only a temporary fix.
• If the pressure exceeds 2.5 bar when heating up, or if water is dripping from the boiler's safety valve, the expansion tank often needs servicing. This is a job for a technician.

2. Switch on the heating mode before the season

Just because the boiler prepares hot water without issue does not mean the heating will work. Heating and hot water circuits operate using different components. Do not wait for the first cold day: switch the boiler to winter mode, turn on the heating for a few hours, and observe:

• Whether the radiators are heating up (if you have hot water but the radiators are cold, the three-way valve or pump is often jammed);
• Whether the screen displays an error code;
• Whether you hear unusual noises (buzzing, knocking, hissing);
• Whether all radiators are heating evenly.

If you notice any problems, it is much easier to resolve them now than in December when your home is already cold.

3. Radiator cold at the top, warm at the bottom? It's time to bleed it

This is the most common problem. When the top of the radiator is cold, air has accumulated inside, and water cannot fully fill the radiator.

How to bleed a radiator yourself:

1. Turn off the boiler and wait for the radiators to cool down.
2. Find the small valve (bleeder valve) in the top corner of the radiator.
3. Place a container or towel underneath.
4. Slowly turn the valve with a special key or screwdriver. You will hear a hissing sound, which means the air is escaping.
5. As soon as water comes out instead of air, close the valve.
6. Check the pressure on the boiler. It often drops after bleeding and may need more water.

If the radiator still doesn't heat up after bleeding, or if the top is warm but the bottom is cold, the problem is likely due to dirt and sediment.

4. System flushing: when is it necessary?

Over the years, rust, sediment, and dirt accumulate in the heating system. This is especially true for older buildings and systems with metal radiators and pipes. As a result:

• Radiators heat unevenly;
• The boiler consumes more gas to produce the same heat;
• The lifespan of the boiler and pump is reduced.

You need a flush if: the lower parts of the radiators are cold, the water coming out of the system is dark or rusty, or the system has not been flushed for several years.

Flushing is a job for a technician. It is done either on the entire system or on a specific problematic radiator, including using a water jet after removing the radiator.

5. Safety: gas and carbon monoxide

A gas boiler is safe if it is functioning properly and the room is properly ventilated. In winter, when windows are closed, the risk increases, so:

• Install a gas and carbon monoxide detector. It will warn you before the danger becomes serious. Carbon monoxide has no color or smell.
• Make sure the chimney/flue is not blocked.
• If you smell gas: shut off the gas valve and open the windows. Do not turn lights or electrical appliances on or off, and do not use fire. Leave the apartment and call your gas supplier's hotline or 112. Do not attempt to repair the boiler yourself.

What you can do yourself and when you need a technician

You can: check the pressure, perform a test run of the boiler, or bleed the radiator.

Call a technician if:

• The boiler won't turn on or shows an error;
• Hot water is available, but the radiators won't heat up;
• Pressure drops consistently or rises excessively;
• Radiators won't heat up even after bleeding;
• The boiler makes unusual noises;
• The issue involves any gas-related components.

Prices: Heating system maintenance in Tbilisi

Prices include labor only, materials not included. The exact price depends on the boiler model and the issue.

Frequently asked questions

Hot water is available, but the radiators are cold. Why?

Hot water and heating operate in the boiler through different circuits. The most common causes are a jammed three-way valve, a stopped pump, air in the system, or low pressure. If the pressure is normal and bleeding did not help, professional diagnostics are needed.

How often should the heating boiler be checked?

It is recommended once a year, before the start of the heating season.

Why does the boiler pressure drop?

The most common reasons are bleeding radiators (pressure naturally drops after air is released), a leak in the system, or a problem with the boiler's expansion tank.

How long does system flushing take?

In a standard apartment with up to 5 radiators, the work usually takes a few hours.

Can I bleed a radiator myself?

Yes, it is a simple procedure. However, the boiler must be turned off and the radiators must be cool. After bleeding, be sure to check the pressure.

Do not wait for the first cold snap. A Profi Masters technician will check your boiler and heating system to prepare it for winter.

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