Why Do I Have Hot Water But No Heating in My Portsmouth Home?
Sadly we see this more often that we’d like – customers calling us because they’ve woken up to a chilly house in the Portsmouth area… but still have hot water from the taps. This may be a common issue many homeowners face, especially as colder weather sets in along the south coast, but luckily, there are thigs that can be done without having to call out a professional. It often comes down to a handful of causes, many of which can be identified — and sometimes even fixed — without too much stress.
We will try and help by exploring some of the main reasons why you might have hot water but no heating, and what steps you can take to get your home warm again.
Common Causes
1. Faulty Diverter Valve
Most combination (combi) boilers — common in Portsmouth’s modern flats and smaller terraced homes — use a diverter valve to switch between heating water for your taps and for your radiators. If this valve gets stuck on the hot water side, you’ll still enjoy a hot shower, but your radiators won’t heat up.
2. Thermostat Issues
Sometimes the problem isn’t the boiler at all. A faulty thermostat or incorrect settings can prevent your heating from kicking in. In some older Portsmouth homes, thermostats may have been installed decades ago and could simply be inaccurate.
3. Air in the Radiators
If your boiler is running but the radiators remain cold, trapped air could be the culprit. This is especially common in period properties around Southsea and North End, where older central heating systems are more prone to airlocks.
4. Low Boiler Pressure
Boilers need the right level of water pressure to circulate heat through the system. If the pressure has dropped (often visible on the gauge at the front of your boiler), your heating won’t function properly even though hot water is still available.
5. Timer or Programmer Settings
If you rely on a heating timer, a power cut or accidental change could mean the heating schedule is off. Portsmouth residents often notice this after storms or grid disruptions along the coast.
How to Fix the Problem
✅ Bleed Your Radiators
If you suspect trapped air, use a radiator key to slowly release the air until water starts to escape. Have an old towel ready — and be careful, the water can be hot.
✅ Check Your Boiler Pressure
Look at the pressure gauge. If it’s below 1 bar, your heating won’t work effectively. You can usually re-pressurise by opening the filling loop valve, but always follow your boiler’s manual.
✅ Test the Thermostat
Turn your thermostat up to maximum. If the heating doesn’t fire up, the thermostat may need new batteries, recalibration, or replacement.
✅ Inspect the Timer/Programmer
Make sure the heating is actually switched on at the times you expect. If there’s been a power cut, you may need to reset the timer.
✅ Call a Gas Safe Engineer for Diverter Valve Issues
If your boiler is producing hot water but never heating, a stuck diverter valve is likely. This is not a DIY job — you’ll need a qualified Gas Safe engineer in Portsmouth to diagnose and replace the valve.
When to Call Us
While some fixes (like bleeding radiators or adjusting pressure) can be done safely by homeowners, anything inside the boiler should only be handled by a Gas Safe registered engineer. Portsmouth has many qualified professionals who can help quickly — especially important as we head into the colder months.
So there you go…
Having hot water but no heating is frustrating, but in many cases, the issue is straightforward. Start with simple checks: thermostat, radiators, and boiler pressure. If the problem points to a diverter valve or another internal fault, don’t risk it — call in a local Gas Safe engineer. That way, you’ll get your Portsmouth home warm and cosy again in no time.
You might also like
