Runs of pipe should be both neat in appearance and accessible for repairs. Forethought will enable you to so place pipe that you can make repairs on all pipes, whether visible or hidden, without having to rip out large portions of your walls or floors.
By grouping pipes in runs, you can confine them to a relatively small area. You can, in addition, install them behind removable panels or in inconspicuous corners in order to facilitate repairs. Do not, however, run water supply pipes too close to outside walls where they will be in danger of being frozen when temperatures drop during winter.
To reduce friction losses, run them as straight as possible and use the minimum number of fittings. This will give you an adequate flow at all fixtures. The friction loss caused by an unnecessary fitting is, on the average, equivalent to 1/10 the friction loss in 100 feet of the same size pipe. Unnecessary dips and bends in horizontal runs may result in air pockets and sediment traps.
Slope, support, valves
If horizontal piping slopes in the general direction of the draining valve, gravity will help clear the pipe when it has to be drained. Whenever possible, all pipes should drain at a single point, usually at a drain cock in the cellar leading to a porous dirt or cinder disposal pit, which makes possible complete clearance of the pipes, if necessary. Where a single drain is impractical, each section of horizontal run should have its own draining point.
The water main usually rises vertically from the meter and is then run along the cellar ceiling. The rightangle bend at which the main, first begins to rise is sometimes fitted with the drain cock through which the entire system can be emptied.
Water pipes are secured to the ceiling by various banging devices, either purchased or made at home from lengths of wood or pipe. Hangers are frequently cushioned with felt or other padding to reduce vibration and noise. Hangers must bold piping securely, but allow for expansion.
Cold-water pipes are run between partitions directly to the fixtures they serve; but hot-water pipes are first routed through a beater or boiler and then run back parallel to, but at least a foot away from, the cold-water piping.
Both hot and cold water pipes should be conveniently valved near the fixtures they serve. These valves enable you to shut off the water supply at one fixture while leaving the rest in operation. These pipes should be supported along their vertical runs by straps or hangers. You should also extend a length of pipe beyond the end of each fixture to provide an air chamber that will cushion the system against water hammer.
Expansion and contraction
Always make allowance for expansion and contraction, especially in hot-water piping. In making branch connections, where fit and position are important, you must compensate for the effects of temperature changes. This is particularly important between two rigid connections which have no give themselves. To prevent undue strain from ruining the connections, place a partial gooseneck or an expansion coil in the pipe line. Allow 1/8" per 10 feet for expansion in copper tubing, and 1/16" per 10 fee in iron pipe.
Cold-water supply lines
Once within the house, the water supply is diverted according to specific needs. Cold water enters the basement supply mains, which act as the house reservoir and supply water to the fixture risers. Risers are the pipes which join the main and rise vertically to points where branches can be run to the various fixtures.
When installing the main and risers, give due consideration to pipe sizes, alignment, and grade so that there is no loss in adequate pressure. Fitting connections, the weakest part of the supply system, should be made carefully. Your runs of pipe should be as straight as possible in order to eliminate unnecessary fittings and reduce internal friction.
The basement supply main should pitch slightly, just a little off level. The maximum grade should be about 1/4" per foot. The lowest point of the cold-water basement main should have a drain cock through which entire system can be drained simply and speedily. If this is not possible, separate drains should be installed a other low points.
Risers which are at right angles to the main should be connected to the main with a 45° connection. The 45° connection will avoid a sudden turn in the direction of the water. Locate valves in places where entire sections can be cut off for repairs. Each fixture group, including lawn sprinkling systems, fire lines, etc., should have its own valve. The water feeding into the hot-water piping must be valved so that the entire hot-water system can be cut off. Finally, there should be a valve which controls the entire house system, just past the water meter.
Hot-water supply lines
Hot- and cold-water lines are installed in much the same way. There are two major differences between them: hot water has a physical effect on the piping, causing it to contract and expand with changes in temperature, and the hot-water lines must run through a heating device and be stored in a hot-water tank.