Any person supplying water within the limits of supply of F1Scottish Water shall furnish such supply to F2Scottish Water as F3it may require and as it is reasonably practicable for that person to provide, and that on such terms and conditions as may be agreed between him and F4Scottish Water ; and, if they fail to agree, the amount of the supply and terms and conditions of the supply shall be determined by the Secretary of State or if he thinks fit, referred for determination to an arbiter appointed by him.