A combi boiler not giving hot water can show up in different ways, from a boiler that has stopped completely to one where the radiators heat up but the tap still runs cold. This guide is for households in Antalya, Turkey whose boiler is running but who can't get hot water. Based on the troubleshooting tables in Vaillant's official user and installation manuals, it walks through the likely causes in order, the checks you can safely do at home, and the point at which you should call an authorized technician.
First, Pin Down the Symptom
The fastest way to the right fix is to be clear about exactly what is happening. Ask yourself:
- Is the boiler completely off, or is the display on and the radiators warm?
- Is there a fault code on the display, such as F.22 or F.28?
- Is there no hot water at all, or is it just lukewarm?
- Is the problem at every tap, or only one tap or the shower?
If only one tap is affected and the others run hot, the boiler is most likely fine; the problem is probably that tap's mixer, its aerator (the small filter at the spout) or its isolation valve.
If the Boiler Isn't Working at All: No Hot Water, Cold Radiators
The troubleshooting table in Vaillant's ecoTEC user manuals lists these causes and remedies for "product not working (no hot water, heating stays cold)":
- Gas isolation valve closed: both the valve on the boiler and any external gas isolation valve must be open.
- Power supply cut: check the fuse box; according to the manual, the boiler restarts automatically when power returns.
- Cold water valve closed: if the cold water isolation valve feeding the boiler is shut, the boiler can't produce hot water.
- Boiler switched off or in standby: restart the unit following the steps in the manual.
If the Display Shows F.22
According to the Vaillant ecoTEC pro manual, when water pressure in the heating circuit falls below 0.5 bar, the boiler shuts down and shows F.22. At that point hot water stops as well as heating. The fix is to top up the system; we explain the correct pressure range and how to top up in what should boiler pressure be.
If the Display Shows F.28
F.28 means the boiler couldn't ignite the burner, which also stops both heating and hot water. After checking the gas valve, you can try resetting up to the number of times the manual allows; see our guides on the Vaillant F.28 error and how to reset a Vaillant boiler.
Radiators Heat Up but There's No Hot Water
If the boiler can provide heating, the gas supply, power and burner are most likely working. The problem is on the domestic hot water side. Check in this order:
1. Hot Water Setting and Mode
In the manuals' troubleshooting table, "hot water temperature set too low and/or hot water circuit switched off" is among the first possible causes. Check the boiler's hot water temperature and make sure hot water operation is on. This setting can change without you noticing, especially after servicing, a power cut or switching between summer and winter modes. If you use a room thermostat or external controller, check that hot water hasn't been switched off there too.
2. Flow at the Tap
In a combi system, the boiler detects water flowing when you open a tap and starts heating it. That requires a minimum flow rate. Vaillant's product brochure says the Aqua Sensor technology in the ecoTEC intro series provides hot water even at flow rates as low as 1.7 litres per minute; a tap opened only slightly, or a blocked aerator, can stay below this model-specific threshold and stop the boiler from firing. Try opening the tap further and cleaning the aerator.
3. Cold Water Inlet and Filter
The Vaillant ecoTEC plus installation and maintenance manual lists a "dirty filter in the cold water inlet" among possible causes of domestic hot water faults. Sand and sediment from the mains can build up in this filter and restrict flow. Because the filter sits at the boiler's connection point, it should be cleaned by an authorized technician.
Causes That Need a Technician
If the problem persists after checking settings, valves and taps, the cause is most likely inside the boiler. The installation and maintenance manual lists these among the causes of hot water faults:
- Scale in the secondary (hot water) heat exchanger: in hard water areas the exchanger gradually clogs, so water comes out lukewarm or the flow drops. The manual notes that the higher the water temperature, the greater the risk of scaling.
- A faulty diverter (three-way) valve: this valve decides whether heated water goes to the radiators or to the hot water heat exchanger. When it sticks, the radiators heat up but the tap stays cold.
- A faulty flow sensor or flow limiter: if the boiler can't detect that a tap has been opened, it won't switch to hot water mode.
- Temperature sensor and wiring: a sensor giving a wrong reading can stop the boiler from heating water enough.
These parts are checked with the unit opened and require genuine spare parts. Unauthorized work on them is risky for both safety and warranty.
Hot Water Arrives but Isn't Enough
Sometimes the issue is capacity, not a fault. If water turns lukewarm when the shower and kitchen tap run at the same time, the boiler's hot water output may not match the household's use. In that case the boiler choice should be reviewed; you can get a rough idea of the right size with our boiler size calculator and ask for a site survey for a firm recommendation.
Quick Checklist
Working through these points in order before calling a technician either solves most problems or lets you give the technician the right information:
- Is the boiler display on, and is a fault code showing? Write it down.
- Are the gas isolation valves under the boiler and on the supply open?
- Is the cold water valve feeding the boiler open?
- Is the water pressure within the range in the manual?
- Is the hot water temperature high enough, and is hot water operation switched on?
- Is the problem at every tap, or only one tap or the shower?
- Is the tap open far enough, and is the aerator blocked?
If everything checks out and there's still no hot water, the problem is most likely inside the boiler; telling the technician which steps you've already tried speeds up diagnosis.
Notes for Antalya
In Antalya, boilers heat the home for only a short winter but produce hot water all year round. That means the heat exchanger, filter and diverter valve on the hot water side work under load for much longer than the heating side. Having these parts checked at the annual service is the most practical way to avoid losing hot water just when you need it most.
Safety Warning
If you smell gas around the boiler, don't try resetting or checking anything. Close the gas valve without touching any electrical switches, open the windows, leave the building and call Enerya Antalya's 187 natural gas emergency line from outside. If you smell flue gas, Vaillant's manual says to open doors and windows, switch the boiler off and call an authorized technician.
As an authorized Vaillant dealer in Antalya, Devka Doğalgaz diagnoses hot water faults on site as part of our boiler maintenance service. If your boiler isn't giving hot water, call us on +90 553 028 82 80 or book a visit through our contact page.
Frequently asked questions
My boiler is on but there's no hot water. Why?
The most common causes are a hot water temperature set too low or hot water mode switched off, too little flow at the tap, a closed cold water valve to the boiler, and internal faults such as a stuck diverter (three-way) valve or a scaled heat exchanger. You can check settings and valves yourself; internal parts are a job for a technician.
Radiators heat up but no hot water comes out. What should I do?
If the boiler can heat, gas and power are most likely fine. Check the hot water temperature setting and hot water mode first, then try more than one tap. If the problem continues, the domestic water filter, heat exchanger or diverter valve needs an authorized technician.
Only one tap has no hot water. Is the boiler faulty?
Usually not. If other taps run hot, the problem is most likely that tap's mixer, aerator or isolation valve. A boiler fault shows the same symptom at every tap.
Will I get hot water if the display shows F.22?
No. According to Vaillant's manuals, when heating circuit pressure falls below 0.5 bar the boiler shuts down and shows F.22, so it won't produce hot water either. The system has to be topped up first.
The hot water is only lukewarm. What can I do?
Check the boiler's hot water temperature setting first. If it's correct and the water is still lukewarm, a scaled heat exchanger, which is common in hard water areas, or a boiler too small for several taps at once may be the cause; an authorized technician should assess it.
