unit; however, protection is not provided when the electrodes are not immersed. Annually, check the anode condition and replace the anodes as necessary. Also, check the current flow; if it has diminished since the previous inspection, the anode probably needs to be renewed. Annually,   in   freezing   climates,   protect electrodes from ice, which may tear them from their hangings or damage them. If ice formation is  severe,  turn  off  the  current,  remove  the electrodes, store them until the freezing season is past, and then reinstall them. Annually, test the effectiveness of the cathodic protection system in one of two ways. 1. Scrape and polish a spot on the tank wall at a point always immersed. At quarterly intervals, lower  the  water  and  inspect  the  spot;  if protection is adequate, the spot will remain uncorroded. 2. Suspend two polished mild steel test plates in the tank at an elevation where they will always be immersed (use No. 6 galvanized steel wire). Ground one plate to the tank wall, but have the other plate insulated from the tank. The extent of corrosion on the grounded plate will come close to the corrosion of the protected tank; the extent of corrosion on the other plate is a measure of the corrosion that would occur if the tank were not  protected. Pneumatic Tanks As  pneumatic  tanks  are  usually  on  smaller installations,  they  may  be  too  small  for  interior inspection,    except  for  observations  through  a removable hand plate. The size, therefore, shows the inspection  procedures  to  be  followed.  Standard inspection procedures are as follows: Quarterly, inspect the air pump and motor to make certain both are operating properly. Check the  operating  record  to  determine  the  time  cycle of air pump operation. If the records show a decreasing time cycle, check for possible air line leaks. Quarterly, check valve operations; particularly, check  the  pressure-relief  valve.  Repair  or replace as necessary. Annually,   check   the   tank   for   signs   of corrosion, both internally and externally. If corrosion  products  are  apparent,  take  the following  action: 1. If the tank is large enough to permit the entry of personnel, paint the inside with corrosion- resistant paint, or line it with cement. If the tank is too small to permit entry, consider changes in operation or in chemical treatment to reduce corrosiveness of water. Corrosion is most likely in areas alternately exposed to air and  water. 2. Paint the exterior as needed. Appurtenances Every  6  months,  ladders,  walkways,  guardrails, handrails, stairways, and risers should be inspected for rust, corrosion, poor anchorage, loose or missing pieces, or other deterioration or damage. Standard inspection procedures include the following: 1. 2. 3. 4. 5. 6. Be sure to check ladders inside as well as outside the tank. Replace worn, corroded, or missing parts; check for deteriorated lugs and rungs as necessary; and, make other repairs to ensure safety  for  the  operators.  Check  revolving ladders  on  the  roof  for  the  condition  of connection  at  the  final  hookups. Ensure that bolts, screws, rivets, and other connections  are  tight. Inspect the condition of the altitude valve vault and the valves for proper operation. Repair, clean, and paint all equipment when necessary. Check the water level indicator for improper operation and repair when necessary. Inspect the cathodic protection equipment and repair when necessary (follow instructions given in previous portions of this chapter). At semiannual intervals, check the electrical connections to lights, cathodic protection, and  so  forth,  for  breaks  in  the  conduit. Remove the conduit inspection plates and examine the internal connections for tightness and adequacy; also check relays for weak springs, worn or pitted contacts, and defective operation. Repair and eliminate all undesirable conditions. 8-31