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Central Heating Cylinders

This web page describes central heating cylinders:

  • What they are.
  • What they do.
  • Common problems.
  • Common fixes.

What They Are And What They Do – Central Heating Cylinders

A central heating cylinder is a water storage tank that heats water; some people call central heating cylinders ‘central heating tanks’.


The cylinder stores hot water for use in the central heating radiators.


Not all central heating systems have cylinders. Some central heating systems have a boiler that heats water when it is needed – there is no need for a cylinder to store hot water.


Central heating cylinder


The image above is a central heating cylinder.


A central heating cylinder is bout 4 feet tall and made of copper, insulating material is then put on the copper.


Central heating cylinders will have a cold water inlet at the bottom and a hot water outlet at the top; cold water in at the bottom, hot water out at the top.


A central heating cylinder will have an electricity supply for the water heating element.


The image below shows a central heating cylinder with the parts labelled.


Central heating cylinder - parts labelled


Common Problems And Common Fixes

All fixes involve draining the cylinder. Always turn off the cylinder electricity supply before trying any fix.


Always check other causes of central heating problems first – replacing or repairing is a big job.


Central heating problems advice.


  • Hot or cold water leak – water sometimes leaks at the cold water inlet or the hot water outlet:
    • Drain the cylinder.
    • Remove the pipe.
    • Apply ‘sealant’ to the pipe join.
    • Replace the pipe.
  • Cylinder not heating water at all:
  • Check the RCD or fuse – reset or replace if necessary.
  • Turn the cylinder electricity supply off.
  • Drain the cylinder.
  • Turn the cylinder electricity supply off.
  • Remove the electricity inlet plug – inspect for damage – clean the plug.
  • Replace the inlet plug.
  • If the problem is not fixed after changing the inlet plug you will probably need a new cylinder.
  • Cylinder heating water but water not very hot:
    • Probably the heating element.
    • Sometimes the heating element is connected to the electricity inlet plug.
    • Turn the cylinder electricity supply off.
    • Drain the cylinder.
    • Remove the electricity inlet plug and heating element – inspect for damage.
      • Clean the heating element.
      • Clean the electricity inlet plug.


Judge Electrical Limited
15 Mulberry Court, Huntington, York, YO32 9TU
Telephone 01904 764845 (Landline), 07919 033113 Mobile)
Email info@judgeelectrical.co.uk
VAT No. 852917405. Company Number 6359328