The cylinder in the airing cupboard is one of the least understood objects in a house, and it decides more about daily comfort than the boiler does: how strong the shower is, how many people can wash in a row, and whether the loft still contains tanks.
Always Plumbing Services works on hot water cylinders across Halesworth, and this is the plain version of the choice.
Vented and unvented, the real difference
A vented cylinder is filled from a tank in the loft and driven by gravity, so pressure depends on the height between tank and tap. It is simple, tolerant of weak incoming mains and cheap to maintain, and it explains why upstairs showers in older houses often disappoint.
An unvented cylinder is sealed and fed straight from the incoming main, delivering hot water at broadly mains pressure everywhere in the house. The loft tanks go, showers improve markedly, and in exchange the system carries safety components and an annual check.
- Vented: gravity fed, simple, height-limited pressure.
- Unvented: mains pressure throughout, no loft tanks.
- Unvented performance still depends on the incoming main.
Sizing to how the household actually washes
Cylinder size is a demand question rather than a house-size one: how many showers happen close together, whether anyone takes baths, and how quickly the cylinder needs to be ready again. An undersized cylinder disappoints on busy mornings; an oversized one heats water nobody uses.
The reheat time matters as much as the volume. A modest cylinder with a quick recovery can serve a busy household better than a large one that takes hours to come back, which is why Always Plumbing Services asks about mornings rather than square footage.
- Count simultaneous demand, not bedrooms.
- Volume and reheat time are one decision.
- Baths dominate the sizing wherever they appear.
The safety kit on an unvented system
A sealed vessel of hot water stores energy, so unvented cylinders carry layered protection: an expansion vessel taking up the water's growth as it heats, pressure and temperature relief valves, and a discharge route able to take any release safely away.
Those components are why unvented cylinders are checked annually. The expansion vessel loses charge over time, relief valves can weep, and the discharge route must stay clear. It is a short visit that keeps a safe appliance safe, and it is not optional maintenance.
When no cylinder is the better answer
A combination boiler heats water as it passes and needs no cylinder at all, which suits households using hot water one outlet at a time and wanting the cupboard back. Its limit is the incoming main: two showers at once is where combis and their owners fall out.
So the honest sequence is demand first, incoming supply second, space third. Always Plumbing Services measures the main and asks about mornings before recommending anything, because the wrong answer here is lived with every day.
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Questions customers ask
Will an unvented cylinder fix my weak shower?
It removes the gravity limitation, so pressure usually improves markedly. It cannot exceed the flow your incoming main delivers, which is why the main is measured before specifying.
How often does an unvented cylinder need checking?
Annually. The expansion vessel charge, relief valves and discharge route all need verifying, and the check is short but genuinely necessary on a sealed system.
What size cylinder do we need?
Sized from real simultaneous demand and how fast it must recover, not from the number of bedrooms. Baths and back-to-back showers are what move the answer.
Demand, then the incoming main, then space: answer those three and the cylinder question answers itself, whichever way it lands.
Always Plumbing Services surveys hot water across Halesworth. The contact page starts with your mornings.
