Water Supply Systems and Sanitary Fixtures
What the domain covers
Water Supply Systems and Sanitary Fixtures tests how water reaches fixtures, how storage and distribution work, and how fixtures such as WC pans, wash basins, sinks and urinals are connected.
Core rules
- A direct system supplies from the mains; an indirect system stores water in an underground sump and an overhead tank before distribution.
- A pump fills the overhead tank; a float valve controls the level; gate valves isolate branches and ball valves give quick shut-off.
- Distribution should avoid cross-connection between drinking water and flush-water lines. Provide an air gap or approved backflow protection.
- Each fixture needs a trap to hold a water seal; fixture outlets and branch sizes must suit the fixture and the available head.
- Pressure depends on head, pipe friction, fittings and valve position. A weak top-floor tap may be caused by low head, a partly closed valve, a clogged aerator or an undersized branch.
Worked example
A top-floor wash-basin tap gives a weak stream while the ground-floor tap is normal. Check the overhead tank level, the branch isolating valve, the aerator and the pipe route. If the tank is full and the valve is open, the likely cause is insufficient head plus friction loss in a long small branch. The reasoning is that pressure falls with height and with flow resistance; replacing a blocked aerator is cheaper to check first than replacing the pipe.
Traps that cost marks
Connecting a flush tank directly to a drinking-water line without protection, using a gate valve for fine flow control, omitting a fixture trap, ignoring available head, and testing only one fixture instead of the whole branch.