Gas Supply Cut by Sibelga in Brussels: How to Safely Restart Your Boiler After an Intervention

Why is gas supply sometimes cut off in Brussels

Sibelga, the operator of Brussels' gas and electricity distribution network, interrupts the natural gas supply for several reasons. It may be a planned cut, announced in advance, for maintenance work or the renewal of pipes in your street. It can also be an accidental cut, following a detected leak, nearby works that have damaged a pipe, or a technical incident on the network.

In both cases, the result for your installation is the same: the gas pressure drops, then disappears entirely from the pipe supplying your boiler. When Sibelga restores the supply, gas returns to your pipework, but air has crept in during the interruption. It is precisely this presence of air that often prevents a boiler from restarting on its own, and which means a precise sequence of steps must be followed before relighting it.

What actually happens in your installation during the cut

When the gas pressure drops to zero, the boiler automatically goes into lockout. This is normal, intended behaviour: the appliance detects the absence of gas and shuts down rather than risk an incomplete ignition or combustion misfires. Most modern boilers then display an error code or a warning light indicating an ignition fault or a loss of flame.

While the network is empty, air infiltrates the pipework, from the meter all the way to the boiler's burner. This air has to be cleared before gas can flow normally again and allow a stable ignition. This is why simply pressing the reset button, without purging first, often fails several times in a row: the boiler tries to light, fails to detect a proper flame because of the residual air, and goes back into lockout.

Before touching anything: the essential checks

Before considering a restart, a few checks are needed. First, confirm that the gas supply has indeed been restored to your street or building. For planned cuts, Sibelga usually communicates the end of the works or intervention by text message, letter, or via its website. For an accidental cut, a Sibelga technician will generally come on site to reopen the meter valve and carry out the checks that fall under their responsibility on the network side.

Next, make sure that the main gas shut-off valve, usually located near the meter, is properly open. Also check that the boiler's own shut-off valve, often located just before the appliance, is open as well. These valves are sometimes closed as a precaution during works, and reopening them is occasionally forgotten.

Finally, visually inspect your installation: there should be no smell of gas near the meter, the fittings, or the boiler. If you detect a gas smell, even a faint one, do not operate any electrical switch, do not bring a flame near, ventilate if possible by opening doors and windows, and contact Sibelga immediately via their gas emergency number. This reflex takes priority over any attempt to restart the boiler.

The restart procedure, step by step

The general approach below applies to the vast majority of wall-mounted gas boilers installed in Brussels, but every brand and model has its own particularities. Your boiler's user manual remains the most reliable reference for details specific to your appliance.

Purging air from the gas circuit

On many recent boilers, air purging happens automatically during the first ignition attempts: the appliance tries, fails, goes into lockout, and it is enough to repeat the cycle a few times for the air to be gradually cleared and for gas to finally reach the burner steadily. On some older models or certain installations, a dedicated purge screw on the gas manifold allows the air to be released manually, but this operation involves the fuel circuit directly and should only be carried out by a trained professional, as it means handling gas in open air, even briefly.

Resetting the boiler

Most boilers have a reset button (often marked "reset" or shown as a circular arrow symbol). After a lockout, pressing this button restarts the ignition cycle. Stick to the number of attempts recommended by the manufacturer, generally limited to two or three close attempts. If the boiler still does not restart after several reasonable attempts, pressing on further does not help and can instead trigger a deeper lockout, or even mask a genuine problem.

Checking the ignition and flame stability

Once the boiler has restarted, check that ignition happens smoothly, without unusual noise, and that the appliance reaches its operating temperature without tripping back into fault mode. If a flame viewing window is present, a steady blue flame is a good sign; a yellow, orange, flickering flame, or one accompanied by soot, is a warning sign that justifies switching off the appliance immediately and calling a professional.

The warning signs that should stop you in your tracks

Certain signs should never be ignored, or played down on the assumption that "it will probably settle down":

• a persistent smell of gas, even a faint one;
• an unusual combustion noise, such as banging or whistling;
• a flame that stays yellow or orange instead of blue;
• black soot marks around the burner or the flue outlet;
• an error code that keeps reappearing despite several resets;
• a carbon monoxide detector going off, if you have one installed.

In any of these situations, shut off the gas supply at the nearest valve, ventilate the room, and contact an approved heating engineer rather than repeating restart attempts. Carbon monoxide is a colourless, odourless gas produced by incomplete combustion: this is precisely why vigilance over flame quality and the absence of unusual noises must remain systematic after every restart, and not only when there is an obvious doubt.

When to call an approved professional rather than persisting alone

Forcing a restart without understanding why the boiler refuses to come back on is never a good idea. Several situations clearly call for the intervention of an approved heating engineer:

• the boiler goes into lockout every time, with no improvement after several reasonable attempts;
• you cannot detect any smell of gas, but the boiler displays an error code you do not understand;
• the appliance restarts but shows one of the warning signs mentioned above;
• your boiler has not been serviced for more than a year, which makes a build-up of residue or fouling more likely to have been revealed by the cut;
• you simply do not feel comfortable handling a gas installation, which is entirely understandable.

In Brussels, periodic servicing of gas boilers is a legal requirement, overseen by Brussels Environment, and must be carried out by an approved technician who issues an inspection certificate. A restart that goes badly after a network cut is often an opportunity to check whether this servicing deadline is up to date, and to arrange a full inspection rather than putting off the problem.

What we do in the event of a Sibelga cut

At DPS Chauffagiste, we regularly intervene across Brussels following planned or accidental gas cuts, for residents who cannot get their boiler running again, or who rightly prefer not to take any risks with a gas installation. Our approach remains systematic: checking that valves are open, fully purging the circuit if needed, a controlled reset, then checking combustion and the airtightness of the whole installation, from the meter through to the flue outlet.

If your boiler does not restart after Sibelga has restored the gas supply, or if it restarts but something seems off, it is better to call us before repeating attempts. A properly carried out restart protects your installation in the long run and, above all, protects your safety and that of your household.