It’s a Tank, inside a Tank

With conventional buffer stores, domestic hot water is provided either through a plate heat exchanger, or a coil tapping within the buffer store. The limitations of this should be clear. The temperature of the domestic hot water is limited by the ability of the heat exchanger to transfer heat from from the buffer water, through the coil. With a high draw-off, cold water may flow faster than it can be heated, you may end up with lukewarm water at the taps. Or, you need higher cylinder temperatures, and correspondingly higher fuel use.


A tank-in-tank cylinder (Also known as a combi-cylinder) is, just that. It’s a domestic hot water tank built inside the buffer store where it can be surrounded by the heating system water. This ensures continuous hot flow, no matter the demand, without requiring high system temperatures and excess fuel use.

Reducing your fuel use, reduces your energy bills.


A Greentherm Tank-in-Tank system saves you money.

Greentherm tank-in-tanks offer:

  • Generic Pricing for Custom Cylinders.
    All Greentherm cylinders are custom made to your exact specifications. We deal directly with the manufacturer, cutting out the middlemen to ensure you get exactly what you need, at a price that suits your budget.
  • 316L Stainless Steel Strength
    Domestic Hot Water tank manufactured from 316L Stainless Steel, for maximum resilience and corrosion resistance.
  • Rapid recovery of domestic hot water with reduced cylinder temperatures.
    Domestic Hot Water tank is surrounded by heating system water, ensuring a rapid recovery of domestic hot water temperatures.
  • Get the best out of your heating systems
    Allows multiple sources of heat to be combined into one store, capable of supplying both your central heating and domestic hot water ensuring no kilowatt-hour goes to waste. Operates at lower temperatures, for maximum efficiency.
  • Flexible installation
    All Greentherm tank-in-tanks feature six configurable tappings in 1″ BSP, along with a single dedicated solar coil, allowing you to use any combination of heat sources in the one installation. Compatible with heat pumps, solid fuel boilers, solar panels and conventional boilers.

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