Brass is typically the preferred choice of water solenoid valves, they are robust, reliable and reasonably cost effective across a wide range of port sizes from 1/8", 1/4", 3/8", 1/2", 3/4", 11/4", 11/2", 2", 21/2" and 3" BSP thread with options for flanged PN16 and ANSI150lb RF flange connection. Brass water solenoid valves are available with NBR standard elastomer sealing with options for EPDM and even Viton, however Viton (FKM) is not considered a suitable option for most water applications. Pressure ranges for this type of mains water control valve depend on function and or size, for example a servo or pressure assisted water solenoid valve will work from 0.5 to 10 bar or more across all port sizes and voltages. However a zero rated or assisted lift / direct acting solenoid valve pressure will depend on port size and control voltage, typically the smaller the valve the higher the working pressure with DC voltages about 30% reduced working pressure range compared to AC control. For example 1/2" BSP 2/2 normally closed brass solenoid valve with 240vAC control will offer 0 to 8.5 bar pressure, where as a 12vDC version will offer 0 to 5 bar pressure range. Most quality solenoid valve manufacturers will offer a simple technical data sheet for all these options, sizes and functions and in some cases will offer high power solenoid coils to achieve mush higher working pressure parameters to suit just about any water application.
However there are applications for cheaper or more cost effective plastic body water solenoid valves, which typically fall into 2 categories.
Domestic appliance water solenoid valves, as found in washing machines, dish washers and automated water facet systems. These cheap plastic nylon bodied valves are designed for short power on valve open periods of 2 minutes maximum with a requirement of a minimum 3 minute no power closed cooling off period. Pressure range 0.2 to 10 bar which covers most mains water supply pressures. Typical sizes 1/4" male or female thread , 3/8" male or female thread or 1/2", 3/4" male thread and 10mm or 12mm hose barb with single, double or triple water outlet. Control voltages from 12vdc, 24vdc and 12vac, 24vac, 110vac and 240vac. Electrical protection is very limited with exposed electrical fas-ton tags.
Commercial or agricultural water solenoid valves, as found in larger commercial washing machines, commercial dish washers, automated water fountain systems and agricultural water systems for animal and cattle water replenishing systems and farm water systems. These plastic nylon bodied valves are designed for 24/7 power on valve open periods with no requirement for closed cooling off period. Pressure range 0.2 to 10 bar which covers most mains water supply pressures, have manual over ride system and flow controller too. Typical sizes 1/2", 3/4", 1", 11/2 and 2" BSP with single outlet. Control voltages from 12vdc, 24vdc, 48vdc, 110vdc, 220vdc and 12vac, 24vac, 48vac, 110vac and 240vac. Electrical protection is very good with IP65 ingress protection and DIN43650A electrical connector.