This system has a main supply feed through a number of valves and is limited to between 350 and 750kpa.
Hot water cylinders of this type are more costly and are less likely to be manufactured of copper. Mains pressure cylinders are usually made of steel. The cold water is sometimes limited to the same pressure that is run through this hot water cylinder thus achieving an equal high pressure system.
These systems have a number of valves to cope with the higher pressure. These may include a shut off valve, a non-return valve, a filter stop cock, a limiting valve calibrated to a set pressure, a cold water relief valve, a tempering valve, and a temper / pressure relief valve.
Normally these valves are purchased together to ensure they are balanced. If they are purchased separately then it is up to the installer to ensure that the valves are the correct pressure.