Undo the headgear nut, using an adjustable spanner. If the nut is difficult to turn, don't force it or you'll risk twisting the base of the tap and putting a strain on the inlet pipe. Instead, pad around the base of the tap with cardboard and use a pipe wrench to grip it firmly as you apply the necessary force to the nut.
Remove the headgear assembly by unscrewing the headgear nut. The washer sits in the jumper, and is either pressed in place (often over a small button) or retained by a nut. If necessary, unscrew the nut that holds the washer in place with an adjustable spanner. Then prise out the old washer, using a screwdriver to dig it out if need be.
Insert a new washer and push it into the jumper, then reassemble the tap in the same sequence. It's a good idea to put a little silicone grease on the threads on the base of the headgear assembly before putting it back in the tap body.
Please visit www.homeekart.com to buy taps, wash basins, bathroom fittings and many more....