WATER SERVICE LEARNING  OBJECTIVE:  Identify  types  of pipe  and  methods  for  measuring,  cutting, joining, and installing water service systems. The water-supply system for a building consists of the  service  pipe,  the  distributing  pipes,  and  the connecting pipes, as well as fittings and control valves. Water carried by  the system must meet accepted standards of purity.  Two major functions of a water distribution system are (1) to carry potable water for domestic use and (2) to provide a high rate of flow for fire fighting. TRENCHING The method of trenching for waterlines is similar to that described earlier for sewer lines. In trenching for waterlines, it is not necessary to set batter boards since great care is not required in laying water pipes to grade because the water is under pressure. The pipes in a waterline may follow the contour of the earth’s surface in a trench that is a minimum of 2 feet deep. Minimum depth of the ditch depends upon the depth of the frost line in the area. The trench should be wide enough to permit ease of working around the pipes and to allow earth to be placed during backfilling. Usually, the trench is not deep enough to require bracing or shoring. Locate the trench at least 4 feet from a previously dug ditch, or trench, to help prevent cave-ins. Water pipes should be laid 1 foot above and 10 feet away from nearby   sewers.  This  helps  prevent  the  water distribution system from becoming contaminated by leaks. Sometimes the water main and sewer lines may cross each other. In such cases, the water pipe must cross over the top of the sewer line, so be careful to make  all  joints  tight;  however,  check  the  local specifications before installing them in this manner. PLACING WATER PIPE 3-28 The distribution system must be kept free from contamination caused by leaks, back siphonage from faulty  plumbing,  and  cross-connections.  The  greatest hazard  in  a  distribution  system  is  cross-connection. This is one physical connection to another that is an unsafe or doubtful source of water or a connection or condition that will permit wastewater to enter the potable public supply. An important phase in the installation of a water system is laying the underground water service pipes. Information to aid you in laying these pipes is provided below. Regardless of the pipe material used, sharp bends and dead ends should be anchored by rodding or concrete anchors. Where the pipe is setting in saddles, metal straps may be used. Even though the pipe is installed within a ditch, the straps help support and hold the pipe in place. Pipe should be founded on solid trench bottoms. Automatic air-release and vacuum valves should be installed at prominent peaks on long supply mains to permit escape of air while the pipe is being  filled  and  entrance  of  air  when  it  is  being drained. Elsewhere in the distribution system, air normally can be released and taken in through service lines. Flow  in water pipes may be achieved by gravity with an elevated tank or by a pumping system. When pipe must be  placed  in a sloping  trench,  the  slope should be as even as possible to keep the pipe from bending and breaking. After the trench is dug, lay the pipe and fittings alongside it. Before you start placing the pipe; shut off the water in the main supply line. The placing should start at the main supply tee. BACKFILLING When you are ready to backfill a ditch, tamp the soil  around  the  pipe  by  hand  or  use  water.  In backfilling,  keep  the  pipe  straight  and  minimize settlement. Soil used to backfill around the pipe should be as free as possible from rocks and debris. When you throw fill material directly on the exposed pipe, you could damage the pipe or move it out of alignment. DROP THE FILL MATERIAL ON BOTH SIDES OF THE PIPE AT THE SAME TIME. When you have water available, use it instead of the tamper, especially when you have a short run to backfill. Fill the ditch completely with loose soil. Attach a piece of pipe to a water hose and push it through the loosely replaced soil until it touches the water main. Turn on the water and let it run until the water appears on the surface. This method allows all the earth to be replaced except the volume equal to that of the pipe. WATER-SUPPLY PIPING Piping materials used in water-supply systems include  cast-iron  pressure  pipe,  copper  pipe, galvanized  pipe,  cement-asbestos  pipe,  ductile  iron pipe, concrete pipe, and PV-class water pipe. Some of the main characteristics of pipe made from these