Hot Water Cylinders UK: Types, Costs & How They Work
Cylinders store hot water for taps and showers. UK system and regular boilers commonly use them; some heat pump systems do too. This guide explains vented vs unvented, costs, and integration.
Vented vs Unvented
Vented uses a header tank; unvented uses mains pressure with safety components like expansion vessels and discharge arrangements.
How They Heat
Indirect coils from the boiler or immersions heat stored water. Insulation reduces standing losses.
Costs
Costs depend on cylinder type, capacity, installation complexity, and any upgrades to pipework or pumps.
When You Need One
Typically with system/regular boilers or high hot water demand designs; combis usually heat water on demand without a separate cylinder.
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Use the Boiler Size CalculatorFrequently Asked Questions
Which is better vented or unvented?
Depends on property and pressure needs—unvented can give strong showers if designed well.
How long do cylinders last?
Many years with maintenance; water quality and anodes matter.
Do cylinders waste energy?
Standing losses exist—choose well-insulated models and sensible sizing.
Can I add a cylinder to a combi?
Usually a major conversion—ask a heating engineer.
What size cylinder do I need?
Based on occupancy and usage—professional sizing is best.