Vented to unvented cylinder conversion
Swap a gravity-fed hot water cylinder and loft tank for a mains-pressure unvented cylinder – stronger showers and no cold water tank in the loft.
Before and after
Before: a vented cylinder is filled by gravity from a cold water tank in the loft. Pressure depends on how high the tank is, so showers upstairs are often weak.
After: an unvented cylinder is fed straight from the cold water main, so hot water comes out at close to mains pressure. The loft tank that fed the old cylinder is no longer needed.
What the survey checks
- Mains pressure and flow rate – an unvented cylinder can only deliver what your incoming main supplies, so we measure both.
- Space for the cylinder, its expansion vessel and the safety valves.
- A safe route for the discharge pipe from the tundish to a suitable outside point.
- How the water is heated – by your boiler (indirect cylinder) or by immersion heaters only (direct cylinder) – and the electrics and controls that need.
- Your heating system – whether it stays open-vented or is converted to a sealed system at the same time.
Safety and regulations
An unvented cylinder stores hot water under pressure, so it has several safety devices and must be fitted by an engineer qualified to install unvented systems (often called G3 qualified). The installation is notified to building control and commissioned, and you receive the paperwork for your records.
Manufacturers recommend a service every year to keep the cylinder safe and its warranty valid.
What happens to the loft tanks
The cold water storage tank that fed the old cylinder can be removed and its pipework capped. If your heating is open-vented, the small feed and expansion tank stays unless the heating is converted to a sealed system – we confirm this at the survey.
Prices
Unvented cylinders are fixed, fully installed from £1,639 (direct) and from £1,769 (indirect). The price includes the new cylinder, installation by an unvented-qualified engineer, commissioning, warranty registration and removal of your old cylinder.
Converting from a vented system needs extra work, such as a new cold main and discharge pipe. That is priced at your free survey, before you commit.