SALT-WATER SYSTEM AT ST. ANDREWS BIOLOGICAL STATION 



127 



tection from siipersatiiration with gases. 

 Although it was generally satisfactory, 

 the rigid intake pipe enclosing the pro- 

 peller shaft must be protected from dam- 

 age from such things as boats, drift ice, 

 and other causes. For example, the shaft 

 of the turbine pump was severely dam- 

 aofed when the former wharf settled sud- 

 denly. An enclosed pumphouse is also 

 required. 



To reduce the possibility of contamina- 

 tion from metal ions, the use of metal is 

 avoided whenever possible (figs. 3 and 4). 



Piping 



Plastic piping of polyethylene and poly- 

 vinyl chloride (PVC) is used throughout 

 the laboratory buildings. There has been 

 no evidence to suggest that either material 

 is toxic. The underground piping is flex- 

 ible polyethylene and is laid below frost 

 level. Rigid piping is used in the labora- 

 tories because fewer supports are required 

 and the sidewalls of the pipes can be 

 tapped to receive stopcocks where 

 required. 



Figure 3. — Hot and cold salt-water, fresh-water, and compressed-air piping along the west wall of 



the basement laboratory. 



