For an indirect system, the cold supply to a shower mixer should come from which source?

• A. Cold water storage cistern
• B. Direct mains cold supply
• C. Boiler feed
• D. A pumped cold water tank

Answer: (A)

In an indirect system, the boiler heats the water and stores it in a hot water cylinder, while the cold supply for taps and mixers comes from a separate cold water storage cistern fed by gravity. This arrangement provides a stable, independent cold feed to the shower mixer and helps prevent any risk of backflow or contamination between the hot and cold sides. Using the cold water storage cistern means the shower can receive a reliable pressure from the stored cold water, even if mains pressure is variable. The boiler feed is part of heating the water, not supplying the cold tap, and a pumped cold tank is not typically needed for standard indirect systems. A direct mains cold supply would be more typical of a direct system, where hot water isn’t stored.