Okla. Stat. tit. 11, § 11-37-120

furnishing water outside limits.

Any municipality owning or operating its own waterworks plant

and every municipality engaged in the distribution of water may

extend its lines beyond the corporate limits of such municipality

and may acquire, construct, own, maintain and operate all necessary

lines, apparatus and equipment, and acquire rights of way, and do

all things necessary and proper in carrying on the business and

furnishing water to any person, firm, corporation or other

municipality beyond the corporate limits of the municipality, to the

same extent as it may now do within the corporate limits of the

municipality. All water so sold and furnished to persons, firms,

corporations and other municipalities beyond and without the

corporate limits of the municipality so selling and furnishing the

same shall be sold and furnished only under written contracts upon

such terms and conditions as may be agreed upon by negotiation

between the municipality and such persons, firms, corporations or

other municipalities. Nothing herein contained shall be construed

to impose any duty or obligation upon any municipality to sell or

furnish water to any person, firm, corporation or municipality

beyond its corporate limits except as the municipality may expressly

undertake by the terms of the written contract.