It is often very desirable to drain a pond, in order to repair its walls, to clean it out, or to replant or take in tender species for the winter. Provision should be made for this. Both outlet and drain may be provided as follows: Lead a large (4- or 6-inch) pipe from the deepest part of the pond to some lower outlet-sewer or stream.
In the pond attach an elbow joint so as to let the pipe turn vertically upward. Screw into the joint a piece of pipe just long enough to reach up to the desired water level. Now, when the tank is full, any overflow may go down the pipe and out. To empty the tank, it is necessary to unscrew the upright piece from the elbow. The outlet should in any case be covered with a wire net to prevent clogging of the drain, to retain fish, and to keep floating plants from being lost.
Should the regular outlet be over a waterfall or dam, a large pipe may be laid in the lower part of this wall. A wooden plug at its inner end will close it on ordinary occasions, and can be removed when the pond is to be emptied. From small ponds the water can be dipped or siphoned out.