Methods Of Testing

Two tests, a roughing test and a final test, should be applied to the drainage system in every building. The roughing test may consist of a water test or an air test, The water test is the one most commonly used, and during warm weather is the most convenient test to apply to the roughing. It cannot, however, be applied conveniently during winter weather in cold climates, on account of the liability of the water freezing and bursting the pipes; even if the pipes are emptied the water-soaked oakum in the hubs is liable to freeze and push the lead calking from the joints.

Fig. 54

The water test is applied by closing all openings to the drainage system, except those above the roof, and filling the system with water until it overflows the vent stacks. It is a more severe test than an air test, also a more unevenly distributed one, the bottom of all stacks ana the house drain being subjected to the full hydrostatic pressure due to the head of water, while the pressure in the soil and waste stacks diminishes in intensity in proportion as it nears the top. To apply a roughing test it is necessary to close all openings to the system. Lead closet bends, and all lead pipes or traps that project from floors or walls should be closed by soldering a round disk of sheet lead over the opening. This should be done at the time of installing the lead work to prevent anything entering the drainage system and also to preserve the shape of the outlets for the walls and floors to be fitted to. Openings to wrought-iron drainage systems and wrought-iron vent pipes can be closed by means of screw plugs or capped nipples. When necessary to extend an outlet from behind a wall or partition, a capped nipple should be used. To close openings in cast-iron pipe, special plugs or stoppers must be used that can be easily removed without jarring the pipe after the system is tested.

Fig. 55

A Testing Plug that is extensively used for closing openings to cast-iron pipe is shown in Fig. 55. It is held in place and made water tight by a rubber band under compression bearing against the inner surface of a pipe or fitting. Testing plugs of this type should be placed inside of the spigot end a of pipe or fitting and not in the hubs b, as the increased surface exposed to the pressure of water or air when placed in a hub increases the liability of the plug blowing out. These plugs are only suitable for testing systems where the head of water does not exceed 50 feet. Where plugs of this type are used, a stop cock c can be substituted for the cap on the end of the handle, and the system can be filled and emptied through the stop cock.

A type of stopper better suited for testing high pressure work is shown in Fig. 56. This type of stopper cannot be blown off under any pressure likely to be encountered in testing drainage systems. When applied to the spigot end of a pipe this stopper must be provided with a collar a to hold the clamps. Stop cocks can be screwed to the capped outlets of these soil pipe plugs through which to fill and empty the system.

Sometimes it is necessary to test a drainage system in cities where tests are not usually applied and soil pipe stoppers are not to be had. Under such conditions plugs can be made by turning some soft wood, like pine or white wood, into the shape of a bung, Fig. 57, and driving them firmly into the outlets. The chief objection to this type of plug is that it must be hammered to loosen it, and the hammering jars the pipe line and might cause a leak.

Fig. 56