The owner or occupier shall guarantee to pay each year to the company, for such period not exceeding 20 years as the company shall determine commencing from the day on which supply is commenced, such sum of money as shall be determined by the company in relation to the estimated capital cost of the extension, but not in any case exceeding 20 percent of that estimated capital cost. If more than 1 consumer is supplied by means of the same extension, each consumer shall guarantee to pay such fraction of the annual guaranteed sum so determined as results from dividing that sum by the number of consumers supplied by the extension:

The company shall credit to every consumer in reduction of any annual sum guaranteed by him in respect of an extension all money paid by him for gas supplied from that extension in the year to which the annual sum relates. The gas shall be supplied at the usual rates for the time being charged by the company:

If any consumer, supplied by means of an extension which supplies other consumers, pays for gas supplied to him from that extension more than the annual sum guaranteed by him, the money so paid in excess of the annual sum shall be applied equally among the other consumers supplied from the same extension who each pay for the gas supplied to them less than the annual sum that each of them has guaranteed, in reduction of their liability:

If at any time an extension for which a guarantee is in force is used by the company to supply gas to any owner or occupier of premises other than premises already supplied by that extension, the liability of existing consumers supplied by the extension shall abate by subtracting from the annual sum which each consumer guarantees to pay the difference between that sum and the resulting sum obtained by dividing the annual guaranteed sum determined by the company pursuant to paragraph (a) of this subsection by the number of consumers, including the owner or occupier of the premises in respect of which the extension is used by the company, supplied by the extension. The company shall do all things necessary to reduce any security given by or on behalf of the existing consumers, and shall make any refund arising from the reduction of any security:

Any owner or occupier of premises requesting the commencement of supply to those premises from an extension for which a guarantee is in force shall guarantee to pay each year to the company, commencing from the day on which supply to the premises is commenced, such fraction of the annual guaranteed sum determined by the company pursuant to paragraph (a) of this subsection to be payable under the guarantee as results from dividing that sum by the number of consumers, including the new owner or occupier to be supplied by the extension, and the liability of existing consumers shall abate proportionately:

If an extension in respect of which a guarantee is in force is, by means of a further extension, used to supply any owner or occupier of premises other than the premises supplied by the existing extension, the company shall require the owner or occupier supplied from the further extension to make, in addition to the annual sum guaranteed in respect of the further extension, a contribution towards the cost of the original extension, which shall be applied equally among the existing consumers in reduction of their liability:

The company shall review the liability of all consumers receiving supply under a guarantee at least once in each year and shall reapportion liability in accordance with this subsection, but not so as to increase any sum guaranteed or to delay any reduction in liability.