The POWERflow, copper unvented hot water cylinder is built to deliver superior mains pressure simultaneously for showers, sinks and wash hand basins. It has revolutionised new build and refurbishment schemes, bringing greater flexibility, increased cost effectiveness and much improved performance.

While the pressure in traditional open vented hot water systems was provided by the head of water from the cold feed cistern, with the POWERflow it comes direct from the cold mains supply.


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Hot Water Cylinder Sizes

Unvented hot water cylinder diagram showing the use of hot water cylinders in the home.

The POWERflow Unvented Hot Water Cylinder offers

  • Proven Reliability
  • Reduced installation costs
  • Can be fitted to utilise sustainable energy - high efficiency solar, ground or air source heat pump coils
  • Increased surface area coils for heat pumps, mean the best utilisation of lower temperature heat pump input
  • Improved shower performance

By using compression fittings and pre-piping the discharge valves, POWERflow is the easiest unvented hot water unit to install and by having an external expansion vessel, is much easier to service and maintain.

POWERflow Unvented Hot Water Cylinder Connections (Boiler Model shown below)

Unvented Cylinder Diagram
Supplied With All Standard Units

  • 22mm Pressure reducing valve set @ 2.1 bar
  • Temp / Press relief valve (Fitted)
  • Expansion relief valve (Fitted)
  • Tundish (Fitted)
  • 50mm Foam insulation
  • Check valve
  • 3kw Immersion heaters. One standard on all indirects. One on 75 + 120 directs. Two on 150 direct upwards.
  • Compression fittings where applicable

Extras Available As Option

  • Solar or heat pump high efficiency coil fitted
  • Connections sited to suit installation
  • Super fast recovery finned copper coil
  • Secondary return
  • Large diameter valves
  • 28mm coil connections
  • Horizontal units
  • Higher pressure units
  • Cased white goods finish

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Interactive 3D Model of 300 litre POWERflow Indirect Unvented Cylinder 


Powerflow Unvented Hot Water Technical Data

For a guide to sizing and dimensions simply visit our sizing page. In addition to our standard sizes we offer a bespoke service creating tailored units - to discuss your options just contact us on 01592 611123 or contact us online.

POWERflow Guarantee

All of our POWERflow unvented hot water cylinders come with a 25 year guarantee.

POWERflow: the leading energy efficient unvented hot water cylinder from Mcdonald Water Storage available across the UK and Ireland.

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Unvented Cylinder Spares

We also stock a variety of unvented cylinder spares. Browse the spares section of our website to see the range. Alternatively our Sales Team are always on hand to help you with your unvented cylinder spares requirements. You can contact them on 01592 611123.

Unvented Hot Water Cylinder Advice