Pull the clear tube out of the top of the coffee maker.

Locate the white plastic 3-way valve at the rear top of the machine. This is the Over Pressure Valve, and controls the pressure of the water flowing into the boiler through a simple spring mechanism. The excess water is returned to the reservoir via the clear plastic tube.

Pull the clip out of the valve that attaches a small tube to the boiler. You'll see that the clip traps a brass collar around the tube into the valve. Pull the tube clear.

Rotate the valve anti-clockwise to unscrew it from the pump. It can be a bit difficult to move.