Solenoid for Ro/Di

[emerald crab]

I use solenoid valves quite a bit. It should be quiet when is on. That one in the picture is a direct action valve. It can become noisy if there is any dirt or anything that would limit the travel of the plunger. If it is a DC valve and you supply it with AC, it will be noisy and it will burn out. If it has a coil for a different voltage, it will do that (that info is printed on the coil). If you use it outside the pressure range that it was build for or if was connected backwards to the water line.