What happens if a domestic cylinder is supplied from a cold water cistern as in-direct cold?

REF: Martyn Bridges’ response to the question “Can a copper cylinder be positioned on its side in the loft under a cold water storage tank? If so how do you support it on its side?”

An ordinary domestic cylinder is constructed in such a way that it is designed to be sited vertically. The top and bottom ends of the cylinder are significantly stronger and of thicker copper material than the sides and it is highly likely a cylinder lying on its side will develop a weakness and potentially “bulge” where the weight is.

There is also a likelihood that the cylinder performance and stratification is seriously affected and as an example a 150 litre capacity cylinder will produce nothing like 150 litres if positioned horizontally.

Finally a 150mm head of pressure is not sufficient to provide a reasonable flow of water and the general recommendation is at least a 1 metre head.

To conclude I would recommend the low pressure cylinder is replaced with either a combi boiler or a mains pressure unvented cylinder, neither of which require a cold water storage cistern to provide it with water.

Question from David Bridge:

With reference to the question regarding the horizontal cylinders, Martyn Bridges recommends changing to a combi or mains pressure vented cylinder. What happens if it is supplied from a cold water cistern as in-direct cold? This is a problem I recently encountered, with very little space to get the required head?

Response from Martyn Bridges:
If the cylinder is supplied from a cold water cistern then this is commonly known as a conventional or traditional hot water system. The third and fourth paragraph of my previous response applies to this type of system, in that if the height or head of the cold water cistern above the cylinder and outlets is insufficient then the pressure will be poor. It is a suggestion to replace the system with a mains pressure cylinder or a combi boiler, neither of which are dependent on a cold water cistern and are fed directly from the water mains.

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