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Heating engineer · Brussels and Wallonia
No hot water, but the heating works
The radiators are hot, but the tap water stays cold or lukewarm. If the boiler heats the house, it's getting gas and power: the problem is in the hot water circuit.
The most common causes
A setting
Hot water mode is off, the temperature is set too low, or a timer limits hot water.
The diverter valve
It sends hot water either to the radiators or to the taps. Stuck on the heating side, there's no hot water.
The flow sensor
On a boiler that heats water on demand, it doesn't notice you've opened the tap.
Scale
It clogs the hot water heat exchanger: the water comes out less and less hot.
The hot water tank
If your hot water comes from a tank, its sensor or setting may be the cause.
What you can check yourself
- On the boiler's display, check that hot water is switched on (« winter » mode or tap symbol) and set high enough.
- Check whether a timer switches hot water off at certain hours.
- Open the hot tap fully: at low flow, some boilers won't fire.
- Try another tap: if only one stays cold, it's that tap or mixer, not the boiler.
- A code on the display? Write it down.
Don't
- Taking the valve or the boiler casing apart.
- Turning the hot water temperature to maximum: above about 60 °C, scale builds up faster and the risk of scalding rises.
Call us if…
- Hot water doesn't come back after these checks.
- The water runs hot, then cold after a few seconds.
- An error code is displayed.
- You only get hot water when the heating is on.
What does a repair cost?
Call-out and diagnosis: €125 excl. VAT. The repair is extra, and you get its price before we start. We usually come within 24 hours (working days) and let you know 1 hour before we arrive.
This advice applies to most boilers. Every appliance has its quirks: if in doubt, your own manual applies, and we're happy to answer on the phone.
Frequently asked questions
I'm a tenant and I've no hot water: who pays for the repair?
Tell your landlord first. Generally, servicing and minor repairs are the tenant's responsibility, and replacing a worn-out or broken appliance the landlord's. Your lease may say more.
Why have I suddenly got no hot water?
Usually a changed setting, a stuck diverter valve or the flow sensor. If the settings are right, call us: it's a common fault, usually fixed in one visit.
Find out more
A breakdown, a question? Get in touch.
Call us or message us on WhatsApp. Or leave your number, with a photo of the boiler if you like: we'll call you back.
