Every leader opening in a gutter must be provided with a strainer to hold back leaves, twigs, etc., and to prevent birds from building nests in the leaders. The best strainers are those constructed of a ball or hemispherical form, like those shown in Figs. 37 and 39.

For ordinary purposes, where the roof water flows to waste, wire ball strainers, put together something like bird cages, are generally used. But in cases where the roof water is gathered into cisterns or tanks, and stored there for domestic use, the strainers must be very close in order to prevent pieces of leaves, etc. from being washed down into the cisterns. Such vegetable matter soon decays and pollutes the water. The strainer b, in Fig. 47, is specially made for this service. It has a very large straining area, which is closely perforated with holes not larger than 1/8 inch.

61. Gutter connections to leader pipes are very important details and should be carefully considered. The offsets necessary for cornice and overhanging gutters should have a good grade from gutter to leader, and should be composed of easy bends - not sharp elbows. Owing to the fact that leaders are liable to freeze, it is advisable to provide outside gutter connections with a slip tube, as shown at a, Fig. 47. This tube is soldered to the gutter lining on top, and is flanged over the face of the soffit of the cornice at the bottom, and thus forms a water-tight channel through which the leader pipe passes. If the leader should freeze and burst between the gutter lining and the soffit of the cornice, this tube will prevent the water from leaking. In the event of the cornice being made of woodwork, such a leak would soon cause the decay of the material.

60 Strainers 425

Fig. 47.

When copper leaders connect with tin-lined gutters, or vice versa, an insulation joint should be made at a convenient point to prevent a too rapid destruction of the metal by galvanic action. Thus, in Fig. 47, a slip joint should be made at c, with a sleeve of tarred or painted burlap inserted between the gutter tube and the leader pipe.