Heating System Troubleshooting

If you think something may be wrong with your heating system, this section can help you solve the problem before you need to contact one of our engineers.

 What is the problem?

• The top section of my radiator is cold
• The bottom section is cold or all radiators are cold or luke-warm
• Only the upstairs radiators are cold
• Only downstairs radiators are cold
• Radiators are cooler in one area of the house
• Radiators are warm upstairs when the heating is off, and the hot water is on
• There’s no heating or hot water
• There’s a sound of gurgling water
• I can hear humming
• I can hear knocks and creaking
• My boiler is noisy

Not sure what the problem is?

Carry out some basic checks using the checklist below

The top section of my radiator is cold

This probably means the radiator needs ‘bleeding'. To bleed your radiator:

• Turn off the heat
• Find the bleed valve, this is usually on oneside near the top
• Place a cloth underneath the bleed valve
• Use a radiator key to gently release the valve and listen for the hiss of air
• Tighten the valve as soon as water begins to flow, and use the cloth to clean up. Take care - the water can be very hot
• Switch the heat back on
• If you find you need to bleed your radiators frequently, you may want to call an NGH heating engineer

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The bottom section is cold or all radiators are cold or luke-warm

This probably means rust or sludge is obstructing the radiator. To clean this you will need to remove the radiator:

• Turn off the heat
• Protect the floor with cloths and have a spanner or pliers, a wrench and a few bowls ready
• Close the valves at each end of the radiator and remove the plastic shield from the ‘lockshield valve', closing it with the spanner or pliers.
• Open the bleed valve near the top of the radiator to allow water to escape. If water keeps running the other valves are not closed properly.
• Use the bowls to catch any water and undo the nuts holding the radiator to the valves on each end. You’ll need to do this slowly.
• Ask someone to help lift the radiator from its brackets
• Drain any remaining water into the bowl
• With the radiator upright, carry it outside
• Stand the radiator on its end, flush out the sludge with a hosepipe before bringing it back in
• Checking the brackets are secure, place the radiator back on the wall and reconnect the nuts
• Open the valves to fill the radiator, then open the bleed valve to allow air to escape and reset the lockshield valve.

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Only the upstairs radiators are cold

This may well mean the cistern in your loft has run dry, because of a jammed or obstructed ball valve. To fix the cistern:

• Clear any obstruction or worn parts
• Check there is enough water to make the ball float when the system is cold.

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Only downstairs radiators are cold

It is likely that the pump is broken. You’ll need to call out an NGH heating engineer.

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Radiators are cooler in one area of the house

This suggests the system is unbalanced. To balance it, you need a pair of radiator thermometers and then:

• Turn off the heat, allowing the system to cool
• Turn on the valves at each end of every radiator, remove the lockshield valve’s plastic cover and turn it using pliers
• Turn the heating back on, checking the order in which the radiators heat up
• Starting with the first radiator, place a thermometer on the pipe at both ends
• Turn off the lockshield valve and gradually turn it back on until there’s almost no difference between the two thermometers
• Repeat on the second radiator and every radiator in turn; when you've finished you'll have a balanced system.

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Radiators are warm upstairs when the heating is off, and the hot water is on

 If you have a gravity-fed system, the check valve is broken.  You will need to call out an NGH heating engineer.

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There’s no heating or hot water

These checks may help you fix the problem:

• Check your power supply is working and a fuse hasn't blown
• Check the gas hasn't been turned off or you have enough oil in your tank
• Check your thermostats and control switches are turned on
• Check the pump is running
• Check the pilot light is lit, your boiler manual will tell you how to relight it

If none of this works, you'll need to call a NGH heating engineer

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There’s a sound of gurgling water

This probably means there's air in the system and the radiator needs ‘bleeding'. Instructions for this can be viewed here.

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I can hear humming

The pump usually causes these noises. These steps should solve the problem:

• Lower the setting on the pump
• Fit the pump on the brackets that absorb its vibrations
• Check the pipes are the right size, to do this you may need to get in an NGH heating engineer

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I can hear knocks and creaking

As pipes expand and contract they rub against joists and walls causing strange noises. To prevent these sounds:

• Find out where the noise is coming from
• Establish where the pipes are rubbing or don't have enough space
• Widen the space around the pipe carefully using a saw or chisel. Too much space might weaken the pipe
• You could use fibreglass insulation to cover the pipes
• In some cases noise can come from unsupported pipes - so secure pipes with a lot of free movement using pipe clips

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My boiler is noisy

Scale and sludge inside, restricted water flow, pockets of steam or even trapped air can cause a noisy boiler. In every case you'll need to call out an NGH heating engineer to find the cause and repair the boiler.

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