Feed and expansion cistern
In plumbing · also called F&E tank
A small cistern, usually in the loft, that keeps an open-vented heating system topped up and gives the water room to expand as it warms. It holds only a little water when the system is cold, so that the level rising on heating up does not reach the warning pipe.
Using Feed and expansion cistern in a plumbing system
Updated
A distinction worth remembering
Most heating faults make sense once you picture the loop: out hot along the flow, through each radiator, back cooler along the return. Then ask how the system is kept full, from a loft tank or through a sealed vessel and gauge.
Questions to take further
- How can I tell whether my heating is sealed or open-vented?
- A sealed system usually has a pressure gauge on or near the boiler and no small tank in the loft feeding the heating. An open-vented one has that loft tank and no pressure gauge to watch.
Sources
- Skills England: plumbing and domestic heating technician — The systems, materials, planning and customer responsibilities in the England occupational standard.
- HSE: domestic gas safety FAQs — Gas Safe registration and checking the categories of work on an engineer's ID card.
Where Feed and expansion cistern fits in the learning path
The Central Heating section covers these topics:
- Wet Central Heating Systems
- Radiators and Heating Controls
- Heating Pressure and Safe Fault Checks
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- Wet Central Heating SystemsCentral Heating
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An open-topped container that holds water at normal air pressure, such as the cold water storage cistern in a loft or the cistern behind a toilet. It is filled through a float-operated valve, and its lid, warning pipe and insulation help keep the stored water clean, stop it overflowing and protect it from frost.
Cistern
Read the Cistern entryCompare related terms
Open a meaning to compare its role with Feed and expansion cistern, or follow its full entry.
Cistern — Cold water storage cistern
An open-topped container that holds water at normal air pressure, such as the cold water storage cistern in a loft or the cistern behind a toilet. It is filled through a float-operated valve, and its lid, warning pipe and insulation help keep the stored water clean, stop it overflowing and protect it from frost.
Read the Cistern entrySealed heating system
A heating system with no loft cistern, filled from the mains through a filling loop and kept under pressure. An expansion vessel absorbs the water's expansion as it heats, a gauge shows the pressure, and a relief valve opens if that pressure climbs too high.
Read the Sealed heating system entryWarning pipe — Overflow
A pipe from a cistern that discharges somewhere easily noticed, such as outside or into the toilet pan, when the water rises above its normal level. Water running from it is a sign that the float valve is not shutting off, and it is there to be noticed and dealt with rather than ignored.
Read the Warning pipe entryBefore you start: some plumbing work is regulated or notifiable
Some water fittings work needs notice to, and consent from, the water supplier before it starts. Check the rules where you live.
Gas work is for competent workers covered by a Gas Safe registered business in Great Britain. Northern Ireland has separate gas regulations. Do not work on gas pipes or appliances yourself.
In England, installing an unvented hot-water system over 15 litres is notifiable building work: use a competent installer registered with a competent-person scheme, or tell building control before work starts. Leave this work to a suitably skilled person.
Wales, Scotland and Northern Ireland have their own water and building rules; check which apply before work starts. Electrical connections belong with an electrician.
This guide does not qualify you or make you competent, approved or registered for plumbing, gas or unvented work.
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