Why It Happens and How to Fix It
If you’ve turned on your taps expecting a warm shower and been met with icy water, but your radiators are happily heating your home, you’re probably dealing with a frustrating issue: combi boiler no hot water but heating. This is a common problem in many homes, and while it can be irritating, understanding why it happens can save you time and potentially prevent damage.
What’s Happening When Your Boiler Heats But Water Stays Cold
A combi boiler works by heating water directly from the mains whenever you turn on a tap. Unlike traditional systems with a hot water cylinder, a combi boiler provides hot water on demand. When your heating works but you have no hot water, it usually points to a fault in the hot water side of the system.
Here are the most common reasons:
Faulty Diverter Valve
Combi boilers have a diverter valve that directs water either to your radiators or your taps. If this valve gets stuck or fails, water may continue to flow to your radiators but never reach your taps.Broken Thermostat or Temperature Sensor
If your boiler’s thermostat or temperature sensor isn’t working properly, it may not signal the boiler to heat water for taps. This can leave your radiators unaffected but results in cold water from your taps.Airlocks or Blockages
Sometimes, air trapped in the pipes or a blockage in the hot water system can prevent water from flowing to your taps. This is less common but can occur, especially in older systems.Low Water Pressure
Many combi boilers require a minimum water pressure to operate the hot water function. If your pressure is too low, your heating may still work while taps fail to deliver hot water.Frozen Condensate Pipe (Winter Issue)
In colder months, the condensate pipe of a combi boiler can freeze, causing the boiler to shut down the hot water supply as a safety measure.
Why You Shouldn’t Try DIY Fixes
It might be tempting to fiddle with the boiler yourself, especially if you enjoy a bit of DIY. But be careful: combi boilers are complicated, high-pressure gas appliances. Attempting to repair them without proper training can cause serious damage or even be dangerous.
Risk of Gas Leaks: Boilers use gas, and tampering with components incorrectly could lead to leaks.
Voiding Your Warranty: Many manufacturers void warranties if an unqualified person attempts repairs.
Further Damage: A small mistake could turn a minor issue into a major, costly repair.
How a Gas Safe Engineer Can Help
If your combi boiler is producing heat but no hot water, the safest solution is to call a Gas Safe registered engineer. These professionals are trained to diagnose the issue correctly and carry out the necessary repairs safely.
Here’s what they typically do:
Check the Diverter Valve: If it’s stuck, they can clean, repair, or replace it.
Inspect Thermostats and Sensors: Ensuring the controls signal the boiler correctly.
Examine the System for Blockages: Removing airlocks or mineral build-up to restore hot water flow.
Verify Water Pressure: Re-pressurising the system safely if needed.
Address Frozen Condensate Pipes: Safely thawing pipes and ensuring proper insulation for winter.
Calling a qualified engineer ensures your boiler is fixed correctly and efficiently, giving you peace of mind and preventing recurring problems.
Quick Tips While Waiting for Repairs
While you wait for your Gas Safe engineer, there are a few safe steps you can take:
Check the Boiler Pressure: Your boiler manual will tell you the safe range (usually around 1–1.5 bar).
Reset the Boiler: Some minor faults can be resolved with a simple reset. Check your boiler manual for instructions.
Turn Off Heating Temporarily: This can prevent unnecessary strain on the system.
Avoid poking around internal components, turning valves you don’t understand, or attempting complicated repairs. It may be tempting, but it could make the problem worse.
A combi boiler providing heat but no hot water usually points to a diverter valve fault, sensor issue, blockage, or low pressure. DIY attempts can be risky, so contacting a Gas Safe registered engineer is the safest way to restore your hot water safely and effectively.
Don’t Wait Get Professional Help
Experiencing combi boiler no hot water but heating can be inconvenient, but it’s not a problem you should ignore. The longer you wait, the more likely a small issue could escalate into an expensive repair or worse, a safety hazard.
If you need a reliable, professional solution, call a Gas Safe engineer today. They’ll diagnose the issue safely, get your hot water flowing again, and ensure your boiler continues running efficiently.