Backwater gate valves, are used on house drainage systems, where the street sewers are so small that excessive rain storms flood the system, and back up into the house drain pipe. The body of the valve is of iron, and the gate valve is made of fine brass, with planed face to make it water and gas-tight. The valve is hung with heavy brass hinges, and in action is automatic, by means of which the flow of sewer water, gas and refuse from the public sewer is prevented from backing up into the house drains. The cover on the inspection clean-out is fastened down to a gasket with heavy screws counter-sunk so as to be flush with the top, and which are easily removed for inspection and flushing purposes.

Fig. 3.

The trap is shown in Fig. 3 with an iron extension man-hole, which extends from the drain in the ground to the surface of the cellar floor, and is provided with a water and gas-tight metal cover bolted to a gasket, which can be easily removed, and which prevents disturbing floors and concrete, when there is any necessity of inspecting the interior. A combination house drain trap and back-water trap with vent opening and inspection opening or a cleanout opening, is shown in Fig. 4. A trap of this type, or, in fact, any trap should be set perfectly level with regard to the water seal. If the inlet to the trap is tipped up, it will not retain enough water to form a water seal, and if the outlet is tipped up, too much water will be retained, and will back up into the drain pipe. These traps should be placed back of the house drain sewer trap and Before the air-vent opening fitting. These gates should never be used instead of a drainage trap, but in connection with same.

Fig. 4.