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Combination tanks are often used where space is at a premium or for ease of installation, reducing the need for a separate cold water cistern.
Where indirect systems are concerned, however, there is usually still a need for a header tank to feed and vent the primary circuit.
This need can be fulfilled by incorporating the header tank with the cold cistern of the combination tank. This is achieved either by inserting a separate smaller tank in the main cold tank (known colloquially as a 'D' tank combination) or splitting the main tank in half (known colloquially as a split tank) In both cases both cold feed tanks have their own cold supply controlled by a ball cock valve.
Using a template as opposite it is relatively easy to indicate the size and positions of your required connections. Heights of tappings are measured from the base of the cylinder to the center of the tapping, their position in the horizontal plane is usually indicated as a position on a clock face or alternatively the distance between tappings is shown.
A worked example is shown for an indirect cylinder, templates are also available for combination units