Local Government Code §232.109

In a subdivision that is not served by fire hydrants as part of a centralized water system certified by the Texas Commission on Environmental Quality as meeting minimum standards for water utility service, the commissioners court may require a limited fire suppression system that requires a developer to construct: (1) for a subdivision of fewer than 50 houses, 2,500 gallons of storage; or (2) for a subdivision of 50 or more houses, 2,500 gallons of storage with a centralized water system or 5,000 gallons of storage.