22 



U. S. BUREAU OF FISHERIES. 



only expensive, but they are also frequently a subsequent source of 

 annoyance, expense, and loss of fish, when damaged as the result of 

 freezing and thawing. It is worthy of special comment, therefore, 

 that H. L. Canfield, superintendent of fish culture at the Fisheries 

 biological station, Fairport, Iowa, has devised a type of pond outlet 

 which has been found, after long trial, to be both relatively inex- 

 pensive of installation and convenient and enduring in operation. 

 The Canfield L outlet, here described and illustrated, provides both 

 for all ordinary overflow and for draining the pond as easily and 

 quickly as with the concrete outlet. 



The outlet consists of two pieces of threaded pipe of required length screwed 

 hand-tight into an elbow. When connected for service one pipe is joined to the 

 dra'nage line, and the other, the elbow acting as a hinge, becomes a movable 

 standpipe, the raising and lowering of which controls the depth of the water 

 in the pond. A pipe stop about 2 feet high is arranged back of the elbow to stay 

 the standpipe from passing the center. 



Two or three cement blocks about 2 by 2 by 2 feet are set about the drainage 

 line to anchor it and to give protection to the embankment against animals 

 and water seepage leading into it along the line. These blocks serve also as 

 couplings for the joining of the pipe to the drainage line and for other con- 

 nections in the line as desired. When a kettle is used one block joins a side 

 of it, anchoring the pipe connection with the drainage line and serving as a 

 base for a walk support. A second block is placed about the drainage line 

 approximately beneath the top and inside edge of the embankment. This is 

 usually a drainage line connection block. If the drainage line passes entirely 

 through the embankment a third block should be placed around it several feet 

 into the embankment from the outside. 



The outlet screen consists of a half coupling (whole coupling if desired) with 

 a quarter-inch groove around it 2 inches below its top, to which is attached, 

 by means of galvanized wire, a covered cylindrical screen of desired mesh, 1 

 foot high. This is screwed to the outlet pipe. A cylindrical or square screen 

 of large proportion may be installed about the standpipe if maximum screen 

 area is needed, although for general use this will not be required. 



A cement kettle 12 by 6 by 1 feet set parallel to the embankment, and within 

 this kettle a small kettle about 15 inches wide, 3 inches deep, and about 7 

 feet long (long enough and wide enough to admit the standpipe with screen, 

 when down level) are used at Fairport with the L outlet. The drainpipe 

 enters the side of the main kettle about 6 inches from the elbow and 1 foot 

 from the end. The bottom of the inner kettle is made level with the base 

 of the outlet pipe when it is down level in position to drain, and provision is 

 made for the removal of the elbow by cupping out the cement beneath it and 

 filling the space with clay, to prevent the trapping of fish when the pond is 

 drained. The main kettle has a slight rise from the inner kettle to the sides 

 to provide drainage, 



A walk of 2-inch plank supported by 2 by 4 inch stringers is made to extend 

 from the embankment to within a foot of the outlet screen, the stringers 

 resting about 6 inches above the top of the outlet pipe when erect. This walk 

 rests on two pipe supports which extend from the cement blocks in the drain- 

 age line. 



The standpipe is chained to the sides of the outer walk support by a piece 

 of galvanized pump chain the length of the distance the pipe travels. This 

 chain passes through a loop eye in the post and is provided with a ring larger 

 than the eye, so that the end of the chain can not be drawn through. By means 

 of this chain the standpipe may be raised and lowered and the level of the 

 water in the ponds adjusted and held as desired. An ordinary lock, or an iron 

 bolt may be used to secure the chain in the loop. 



Malleable iron pipe is excellent material for the outlet, but ordinary black 

 steel pipe is cheaper and gives good service. One piece of pipe of required 

 length for the standpipe, threaded both ends, an elbow, and about 2 to 2i 

 feet of pipe threaded one end, to serve as connecting pipe with the drainage 

 line, are all the materials required for the outlet. It is recommended, how- 

 ever, that metal pipe be provided from the elbow well into the embankment 

 for the better protection of the drainage line. Eight-inch pipe is recommended 

 for ponds of 1 acre in area and proportionately smaller pipe for smaller ponds. 



