How to fix hot water but no heating. 5 troubleshooting tips from an engineer.

Key takeaways

Learn five simple boiler tests for when your radiators are not working but your hot water is:

🔥 Check your boiler pressure

🔥 Check your thermostat

🔥 Check your radiators 

🔥 Check for leaks

🔥 Check your diverter valve

If you feel uncomfortable doing these inspections or if your problem persists, please call a qualified engineer.

Only when your heating stops working do you realise how important your boiler is in creating a cosy home. Fortunately, BOXT’s experts have shared five quick and easy tests to help you diagnose and fix your issue. To get started…

1. Check your boiler pressure

Problem:

If your boiler pressure or system water pressure is low, the water inside can’t circulate through your central heating system efficiently.

How to fix:

Locate your boiler's pressure gauge and check the needle rests between 1 and 2 bar. If it's lower than this, and the needle is in the 'red' area, top it up by opening the filling valve or using a loop – please follow your manufacturer's guidance to do so. You may need to reset your boiler, but once actioned your boiler should resume working once the pressure hits the right level.

Check your thermostat

Problem:

A faulty thermostat, or one that’s been incorrectly programmed, might prevent your heating system from operating how it should.

How to fix:

Start by checking that your thermostat is switched on or turned up. Then, ensure the timer and temperature functions are both programmed correctly. Next, if your thermostat is battery-operated, try changing the batteries. If that doesn’t resolve your issue, then your thermostat could be faulty.

If you have a Hive Thermostat, try switching it off at the wall, waiting for 10 seconds and then switching it back on. Allow 10 minutes for the hub to reboot, then refresh your app’s dashboard. For more help, call Hive support on 0333 202 9614.

Check your radiators

Problem:

Sludge, debris, and trapped air can clog up radiators, leaving your hot water working but with no heating.

How to fix:

While your heating is switched on, feel your radiators for any cold spots. If you find any at the top, bleed your radiators to release the trapped air. Then, repressurise your system afterwards if needed, ensuring the radiator valves are turned on at both sides. If this doesn't work, the system may need cleaning to flush out any sludge or blockages that have built up over time.

Alternatively, if you have thermostatic radiator valves, try turning them up to number 5 and waiting a few minutes. If your radiators don't warm up but you can hear the boiler working, they could be faulty, in which case an engineer will need to repair or replace them.

Check for leaks

Problem:

Any kind of boiler water leak could leave you with low pressure, leading to insufficient hot water and system faults that may cause further damage to your appliance and property over time.

How to fix:

Check under and around your boiler and radiators for drips, pools, or patches of water. Take particular care when checking pipe connections.

Please never attempt to open your boiler unit. Contact your local Gas Safe registered engineer if you find any damp patches.

Check your diverter valve

Problem:

Diverter valves control the water flow between a combi boiler's heating and hot water systems. Over time, this valve can break or get stuck in one position, leaving your hot water on but no heating coming out.

How to fix:

If your diverter valve has developed an issue, hot water won't be able to reach your radiators. The only safe way to fix this issue is by calling your local Gas Safe registered engineer who will perform a repair or replacement.

Still no heating?

If you've carried out these checks and your central heating isn’t working but the hot water is, it's time to contact a heating professional.

BOXT's team of local Gas Safe registered engineers can be with you as soon as the next working day when booked before 3pm. Visit this link to book your one-hour callout for a fixed price of £89. Alternatively, you can speak with our sales team on 0800 193 7777, or get in touch via Live Chat.