The Stored System (a guide):This type of water storage system takes the direct cold water supply straight into the cold-water storage cylinder in the loft space. The storage cylinder is normally fitted high up in a property, usually in the loft space. The cylinder feeds the taps, and although you isolate the water supply these taps carry on running and dont stop for a while. This can be up to half an hour for the flow to stop if the cylinder is big, so you need to know where the isolating valves are, to allow you to turn the water off immediately. Clapham Plumbers are a professional service who know this type of system.The Mains System (a guide):The cold water supply in a high-pressure system, is fed straight from a main water feed, which means that if you turn off the main stop tap the water will stop almost immediately. This cold (main) water is also used to move your hot water from the hot taps. If you should turn off the main stop tap, it will isolate the pressure from the hot water, so there is no hot water at the tap. If no cold water mains pressure is pushing hot the water through, it cannot reach the taps and stays in the hot water cylinder (if it is fitted). The majority of properties have a mixture of both the mains and the stored fed water, Example: Cold water from the mains is fed to the kitchen then from a storage cylinder to a bathroom, with all the hot water coming from the stored supply. A Clapham Plumber is skilled and can on both systems.A). The important advantage of a high-pressure system is when the main stop is isolated it will stop all hot and cold water flowing straight away. B). The disadvantage is a large mass of water will leak out if you dont know where to isolate the main stop.