SALT-WATER SYSTEM AT U.S. LABORATORY, BEAUFORT, N.C. 



121 



minute at the same head. All pipes are 

 2-inch flexible polyethylene plastic except 

 at laboratory water tables and outside 

 tanks. Here semirio;id plastic pipe is used 

 since it can be tapped for petcocks at the 

 water tables and is self-supporting at the 

 outside tanks. One-inch pipes are used 

 at the laboratoi-y tables, and at the out- 

 side tanks l^y^-inch pipes are used. Tlie 

 foot valve and pipeline valves are of rigid 

 plastic with polyethylene diaphragms. 



An overflow standpipe 18 feet at top 

 elevation above the pump mamtains con- 

 stant pressure in the system regardless of 

 how much water is being used, within the 

 capacity of the pump. Excess water flows 

 from the top of the standpipe, and as long 

 as some water is overflowing, the pressure 

 at all outlets at tanks and water tables 

 remains constant regardless of where 

 valves are opened or closed. The top ele- 

 vation of the standpipe is 12 feet above 

 the highest outlet on the system. Of 

 course, if outlets at higher elevations are 

 desired, such as in a second-floor labora- 

 tory, the height of the standpipe would 

 have to be increased to above the outlet 

 height to increase the pressure so that 

 water would rise to the higher elevation. 

 In our installation the top of the stand- 

 pipe is extended 2 feet above the overflow 

 pipe to accommodate surges of water when 

 the pump is first started. 



Hard-rubber pumps must not be al- 

 lowed to run dry, as this will ruin the 

 pump shaft and seals. Therefore, as a 

 safety precaution a pressure-operated 

 switch is inserted in the electrical power 

 lines to the pump so that it will be stopped 

 automatically if water is not being 

 pumped. This has proved useful many 

 times when the foot valve has become 

 clogged, as by a piece of plastic sheeting, 

 and also has prevented the pump from re- 

 starting when the pump and lines have 

 drained dry after a prolonged power 

 failure. 



To facilitate the pumping operation 

 when the lines are empty, a valve with a 

 fitting to which a garden hose can be at- 

 tached is located near the standpipe. The 

 standpipe, pump, and suction line can 

 then be filled with fresh water from a 

 near-by fresh-water spigot before start- 

 ing the pump. 



Since this system is nontoxic to marine 

 organisms, considerable growth occurs 

 within the plastic pipes, thus reducing 

 the amomit of water that is transported. 

 The rate of fouling of salt-water systems 

 probably depends upon latitude of the in- 

 stallation and local conditions. In this 

 area it is necessary to clean the system 

 about twice a year. This is accomplished 

 by stopping the pump and allowing the 

 water to remain in the system for about 

 a week until all organisms are dead. Soft 

 forms usually can then be flushed out by 

 starting the pump, opening all valves and 

 drains, and removing pipe caps from the 

 supply at the water tables. 



About once a year the setting of hard- 

 shelled animals, such as oysters and bar- 

 nacles, clogs the pipe to such an extent 

 that acid must be used to dissolve or 

 loosen them. Commercial hydrochloric 

 acid diluted to about 10 percent (1 part 

 acid, 3 parts water) is introduced into the 

 standpipe, and all outlet valves are 

 opened slightly until the dilute acid 

 reaches all parts of the system. The acid 

 solution is allowed to remain in the pipes 

 for approximately 48 hours and the pipes 

 can then be flushed clean. 



The outside tanks are made of concrete 

 w^ith inside measurements of 6 feet by 16 

 feet with depth of 30 inches at the ends 

 and 31 inches near the center (figs. 2 and 

 3). Notches on the sides allow vertical 

 screen partitions to be inserted so that 

 the tank can be divided into four com- 

 partments. A 4-inch pipe nipple cast into 

 the bottom accommodates standpipe over- 



