Zone valve
In plumbing
A motorised valve that opens and closes to send heating water to one part of a system, such as the radiators or the hot-water cylinder. A layout with two two-port zone valves is often called S-plan, and one using a single three-port mid-position valve is often called Y-plan.
Using Zone valve 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 Zone valve 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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Recall a related term
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The pump that pushes water round a wet heating system, out from the boiler along the flow and back along the return. In many combi and system boilers it is built in; in older systems it sits on the pipework, often near the cylinder. A pump that has stopped leaves the boiler hot and the radiators cold.
Circulating pump
Read the Circulating pump entryCompare related terms
Open a meaning to compare its role with Zone valve, or follow its full entry.
Circulating pump
The pump that pushes water round a wet heating system, out from the boiler along the flow and back along the return. In many combi and system boilers it is built in; in older systems it sits on the pipework, often near the cylinder. A pump that has stopped leaves the boiler hot and the radiators cold.
Read the Circulating pump entryWet central heating
A heating system that warms water, usually in a boiler or heat pump, and pumps it through pipes to radiators or underfloor loops, where it gives up its heat before going back to be warmed again. Most homes with a gas boiler in Great Britain are heated this way.
Read the Wet central heating 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.
A definition is a start. Using it in a real question is where it sticks.