Water heating system All aspects of plumbing questions and answers, help, tips and information

[dinkydunc]

I'm used to a combi boiler for heating water and have moved into an older property where there is a small square tank mounted above a cylinder in the airing cupboad. The water can be heated by the boiler or an immersion heater. Got two questions -1) why is there both a square tank and cylinder? 2) is it cheaper to heat water with the boiler (gas) or the immersion (electricity)? Many thanks

[Steve the gas]

Hi,

You have both facilties in case one fails.
Iirc gas is cheaper but then are you on an economy 7 tariff?

[Dave From Leeds]

Steve has answered your second question. To answer the first one, the hot water, once heated is stored in the cylinder. When you open a hot tap, some of this water is pushed out by the head of cold water in the square tank. This feeds in at the bottom of the cylinder and the hot water comes out at the top. Have a look at the diagram of an indirect cylinder on this site. The cold water comes in from the square tank (cold water storage tank) at point 2 and the hot goes out to the taps via point 7