1. Use the diameter of the tank, the distance from largest loop to ringwall, and anode spacing to determine the number and diameters of anode loops required.
2. Calculate the required total anode length. This is the sum of the circumferences of the loops plus the steps from each loop to the next smaller loop. Steps from one loop to the next smaller loop are assumed to be at 45 degrees so the length of each such step is sqrt(2) times anode spacing.
3. Divide the required total anode length by 50 and round up to determine the number of anodes required. The number of anodes required times 50 is the actual length of anode.
4. Make the assumption that a safety factor of 20 ft should be provided with each order.
5. If the difference between the required anode length and the actual anode length is less than 20, increase the number of anodes by 1. Recalculate the actual anode length.
6. If the diameter of the smallest loop is greater than or equal to the anode spacing AND the difference between the required anode length and the actual anode length is less than or equal to 40 ft., increase the number of anodes by 1. Recalculate the actual anode length.

Notes:

1. If the diameter of the smallest loop is greater than or equal to the anode spacing , a smaller loop or some other configuration must be provided to protect the center of the tank.
2. The 40 ft criteria allows enough anode to construct a loop of 3 ft. diameter plus the 20 ft. safety factor.
3. Required materials based on a single circuit with a power feed on each end and intermediate tee feeds as required. Tee-end feeds are recommended every 1,000 ft. (300 m). One reference electrode is recommended for every 50 feet (15 m) of tank diameter.
4. Pt and MMO perform the same in this application. Choice is based on personal preference.
5. Estimates based on 1/3 man-hr. per anode. Experienced crews should take less time.
6. These calculations are based on protecting only one surface. If two surfaces are being protected, double the desired current density.