One branch leading off the cold water main is lirected to the hot water storage tank. Like other fixtures, the entrance pipe is fitted with a shutoff valve to isolate it if necessary. The tank itself is also fitted with a drain valve to enable the tank to be emptied for repairs or cleaning out any sediment ;hat may accumulate in the bottom of the tank. The water held in the tank is heated by electric elements )r by a gas flame.
Because the water enters the hot-water tank under the same pressure as the rest of the cold water system, it also leaves the tank under the same pressure. It is directed throughout the house to all the lot water faucets and fixtures through a network of pipes similar to the cold water system. The hot-water tank is equipped with a thermostat which regulates the temperature of the water in the tank.
In case the thermostat is faulty, each hot-water tank also has an emergency relief valve which automatically opens to release overheated water before it can boil, which would explode the tank. Phe overheated water is run harmlessly into a drain Ind out to the sewer.
Drain – waste – vent system
Once the clean water has been used, it must be directed back to the sewer system efficiently and hygienically. Although water is supplied and reaches fixtures under pressure, the flow for drainage is entirely dependent on gravity. Therefore the pipes involved are of a much greater diameter than the supply pipes and must run downward at a slight angle, usually about 0.25 in. (6 mm) for every foot, to assist the flow of water.