When a water inlet solenoid is in the de-energised state The plunger is pushed down over the central hole see fig 5a.

Water pressure from the supply feeds through the bleed hole into the plunger chamber, forcing the rubber seal to shut off the outlet from the valve. Fig 5e

When the valve is energised the plunger is withdrawn from the central hole allowing water to flow through into the outlet, this causes a the water pressure in the plunger chamber to fall.

When the pressure falls the inlet water supply lifts the rubber seal from the outlet port of the valve and water flows. Fig 5f

When the valve becomes de-energised, the plunger falls back and covers the central hole in the rubber seal.
Water enters the plunger chamber increasing the pressure to the point where the seal is forced down and cuts off the water flow. Fig 5e

Fig 5e

Fig 5f