MegafloIndirect Hot Water Cylinders

An indirect cylinder is heated via a coil connected to a boiler or heat source, keeping the boiler circuit separate from the stored hot water. A direct cylinder heats the water itself using an immersion element only. Indirect Megaflo cylinders are the usual choice where you already have (or plan to fit) a gas or oil boiler, as they recover heat faster and cost less to run.

As a rough guide, a 1-2 bedroom home with one bathroom typically suits a 150-210 litre cylinder, while a 3-4 bedroom house with two bathrooms usually needs 210-300 litres. Properties with power showers, multiple en-suites, or high simultaneous demand should size up rather than down. If you're unsure, it's worth checking litres-per-minute output against your incoming mains flow rate before committing.

Yes — unvented cylinders like Megaflo fall under Part G of the Building Regulations and must be installed by a competent person, typically someone holding a valid G3 unvented hot water certificate. The installer needs to notify Building Control (directly or via a registered scheme) and commission the cylinder correctly, including setting the discharge pipework and safety valves. Fitting one without proper certification can cause issues at sale or with insurance.

Many Megaflo indirect models are available with twin coils, allowing one coil to take heat from a boiler or heat pump and the second from solar thermal panels. This lets the solar contribution do the bulk of the heating in summer, with the secondary source topping up when needed. Always check the specific model's coil configuration and heat exchanger area against your solar or heat pump output before ordering.

Most Megaflo indirect cylinders are designed for vertical installation, standing on the floor with pipework connections at the top and base, and this is the standard configuration for airing cupboards or utility rooms. Horizontal models exist for loft spaces or properties with restricted ceiling height, but they're a different product line, not just a cylinder laid on its side. Check the specification carefully, as horizontal units often have a different maximum capacity and coil layout.

Yes — manufacturers recommend an annual service to check the expansion vessel pre-charge, temperature and pressure relief valve, and other safety components are functioning correctly. This should be carried out by a G3-qualified engineer, and keeping records is sensible for warranty purposes and any future property sale. Neglecting servicing is one of the most common causes of premature valve failure or nuisance dripping from the discharge pipe.