What is Mains Pressure? - Rheem
Mains pressure is the pressure that is delivered to your home from the street’s water main, so is the highest flow possible to your taps. Because of its higher pressure, it can deliver a strong flow to many taps or showers at once. And as both the cold and hot water are at the same pressure, it ensures a strong flow which is easily mixed to find the right temperature.
Storage water heaters provide mains pressure water. Continuous flow water heaters may need to reduce the pressure so that the water can be heated to full temperature, so they deliver at less than mains pressure (but for most things, you won’t notice the difference).