Practical work: repairing a simple mixer tap
A mixer tap mixes hot and cold water to give a flow at the temperature you want. A single-lever mixer has a metal body, a cartridge, a nut that holds the cartridge, a decorative cap, a handle, rubber rings and, at the outlet, an aerator (a protective mesh). Before repair, the water supply to the tap is shut off with the valves; then an adult prises out the cap plug and loosens the screw, removes the handle, and unscrews the nut with a wrench to take out the cartridge. The old cartridge is not thrown away: it is taken to the shop so the new one can be chosen by diameter and height. The cartridge seat is cleaned with a soft cloth, the locating tabs of the new cartridge go into the matching recesses, and the tap is reassembled in reverse order. If the aerator mesh is clogged, it is unscrewed and rinsed, and the mesh is replaced if needed; the water is turned on slowly to check for leaks.
Arrange name cards of 8 parts of the tap in the order of repair (cap, screw, handle, decorative cover, nut, cartridge ...). On a real tap the valve must be shut first; an adult or the teacher does the work while pupils hand tools and follow the sequence.