No Hot Water From the Boiler: 5 Home Checks
Independent guide — no official affiliation with the platforms mentioned.
Short answer
If radiators heat but taps give no hot water, check in order: summer/winter mode, water pressure (1-2 bar), gas valve, tap filter/flow sensor and debris filters. The most common causes are low pressure or the wrong mode; filling to 1.5 bar with the filling loop and resetting restores hot water in most cases. If heat does not hold, a flow sensor or three-way valve fault requires service.
01 — Step-by-step fix
Step-by-step fix
STEP 01
Check summer/winter mode
Is the tap (summer) symbol selected on the panel? On some models no hot water is expected with winter-only settings; the wrong mode is the most overlooked cause. Turn the mode dial to the tap symbol.
STEP 02
Check water pressure
Pressure should read 1-2 bar; below ~0.5 bar the boiler will not produce hot water for safety. Open the filling loop slowly to reach 1.5 bar and close it fully. Continuous drops need leak/expansion vessel checks.
STEP 03
Check gas valve and power
Ensure the gas valve is open; valves sometimes remain closed after a gas outage. Check the boiler's power and fuse; short outages can lock the boiler — unplug for a minute to reset.
STEP 04
Clean the tap and flow filter
If only one tap has weak hot water, the aerator may be scaled. A scaled inlet filter at the boiler reduces flow and prevents ignition; this cleaning is a simple DIY step.
STEP 05
If still failing — flow sensor or three-way valve
If everything above is fine and the boiler ignites but water stays cold, the flow sensor or three-way valve may be faulty; these need service. If the boiler never ignites and shows an E/F code, note the code for the technician.
Listen for ignition clicks: if the boiler clicks, gas/ignition is trying; no sound points to the flow sensor as the likely culprit.
Tips
- In hard-water areas, annual service greatly reduces hot water faults; exchanger scale is the most common cause.
- If the boiler sits inside a cabinet, poor ventilation causes overheating; do not block the cabinet door.
- If you noticed the issue at summer start, check the mode — winter-to-summer switching is often forgotten.
02 — Frequently asked questions
Frequently asked questions
Radiators heat but no hot water — why?
That is the classic three-way valve or flow sensor fault: the boiler works in heating mode but does not switch to the hot water side. After mode and pressure checks, call authorized service if it persists.
Hot water comes then goes cold — why?
Usually a condensate/pump or partial three-way valve fault; the boiler may be tripping into overheat protection. Very low flow also feels similar due to modulation limits — increase flow slightly at the tap.
Pressure keeps dropping — is it related to hot water?
It can be. A half-closed filling loop bounces pressure and trips protection. Close it fully and monitor for 24 hours; continuing drops mean a leak or expansion vessel fault requiring service.
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Links in this guide point to official platform pages. Steps may change with platform updates; check the page date.
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