The generator needs a 15mm cold water supply (warm water can also be used) with a minimum pressure of 6-foot head or 0.2 bar. This is because the water inlet solenoid on the generator needs a small amount of pressure to work. If there is less than 0.2 bar pressure, the steam generator will not work, or may only work intermittently, as it fills up with water very slowly.
It is very unlikely that the water pressure in a house will be this low. However, there is one instance you should be aware of, which is when the generator is located in a loft area and the water supply comes from a tank which is also in the loft – here the water has not dropped far enough to create any pressure. In this instance, the water supply should be taken from the supply to the water tank, rather from the tank itself.
Ideally, the pressure should not exceed 1 bar or 33.5 foot of head, this is because if the pressure is too high, the bather may hear the noise of a rush of cold water hitting the boiling contents of the generator tank. If the only water supply available is at high pressure, the installer should fit a pressure-reducing valve (this is an item that can be bought from any plumbers’ merchant).
Some commercial installations, where the steam generator is working many hours per day, require a water softener to filter out any impurities such as lime scale or chalk. However, in a domestic application only the worst water would need filtering. The rule is that if other water-fed equipment (such as a washing machine or kettle) is OK, then no filtering is required.
Some houses get their water from a borehole supply, which tend to be very chalky. In this case a water softener should be used.