Artikel 71

Water-ballast spaces include water-ballast tanks in the double bottom and all water-ballast spaces outside the double bottom, below the upper deck (e.g. forward and after peak-tanks, deep-tanks and coffer-dams), when the said spaces comply with the regulations indicated below.
On an application in writing from the owner, and subject to the limitations indicated hereafter, spaces not exempted which are appropriated to and exclusively used for water-ballast shall be deducted from the gross tonnage, provided that they fulfil the following conditions:
(a) That they are certified as properly constructed and tested ballast tanks;
(b) That they are solely adapted for water-ballast, however, a peak-tank shall also be deducted when adapted for carrying fresh water for the ship's own use;
(c) That their only means of entrance shall be ordinary size manholes.
Ad (a): – The expression “properly constructed and tested ballast tanks” indicates that the tanks are able to stand pressure under a head of water. The filling of the openings in the tank-top around the frames at the sides with cement is not permissible.
Ad (b): – The means for filling and emptying water-ballast tanks (e.g., pumps, pipes, etc.) must be of a permanent and satisfactory character and independent of the installations for water or oil for motor cooling, water for feed or domestic purposes, fuel oil or cargo, however, as regards a peak-tank, connection with the installations for fresh water for the ship's own use will not disqualify the tank as a ballast tank. Pumping installations must be of suitable type and dimensions for dealing efficiently with the water-ballast. The suction and delivery pipes shall, in general, not be less than 2 1/1 inches, or 64 mm., inside diameter. Hand pumps, portable pumps, or hose connections are not to be regarded as permanent and satisfactory means for filling and emptying. In all ships not exceeding 200 tons, or 566,57 cubic metres gross, and in ships over 200 tons, or 566,57 cubic metres, having sails as principal means of propulsion, hand pumps, constituting the only means for filling or emptying water-ballast spaces, will not be objected to, provided that the installation is of a permanent character.
Ad (c): – The manholes shall have an area not exceeding 2,5 square feet, or 0.232 square metre.
Coffer-dams shall be considered as water-ballast spaces, provided that they fulfil the foregoing conditions.
Double bottom tanks connected with the ballast-pumping system, or available for water or oil for motor cooling, water for boiler feeding, or domestic purposes or for carrying fuel oil or cargo, shall be considered as water-ballast spaces when determining the allowance for the same.
For the purpose of calculating the cubic capacity of the deductible water-ballast spaces, it should be noted that the total cubic capacity of water-ballast spaces below the upper deck which are exempted or deducted (including whole or partial double bottom, peak-tanks, deep-tanks, coffer-dams and all other types of bona fide water-ballast tanks) shall not exceed 19 per cent of the gross tonnage. In case the cubic capacity of exempted water-ballast spaces in the double bottom equals or exceeds 19 per cent of the gross tonnage, no deduction for water-ballast spaces may be granted. A part of a tank may be allowed as a deduction, provided that the whole tank is fitted, constructed and tested for carrying water-ballast.