(a) The commission shall establish recommended standards relating to the domestic use of harvested rainwater, including health and safety standards for treatment and collection methods for harvested rainwater intended for drinking, cooking, or bathing.
(b) The commission by rule shall provide that if a structure has a rainwater harvesting system and uses a public water supply for an auxiliary water source, the structure must have appropriate cross-connection safeguards.

(b-1) A privately owned rainwater harvesting system with a capacity of more than 500 gallons that has an auxiliary water supply shall have a backflow prevention assembly or an air gap installed at the storage facility for the harvested rainwater to ensure physical separation between the rainwater harvesting system and the auxiliary water supply. A rainwater harvesting system that meets the requirements of this subsection is considered connected to a public water supply system only for purposes of compliance with minimum water system capacity requirements as determined by commission rule.
(b-2) A person who installs and maintains rainwater harvesting systems that are connected to a public water supply system and are used for potable purposes must be licensed by the Texas State Board of Plumbing Examiners as a master plumber or journeyman plumber and hold an endorsement issued by the board as a water supply protection specialist.
(b-3) A person who intends to use a public water supply system as an auxiliary water source must give written notice of that intention to the municipality in which the rainwater harvesting system is located or the owner or operator of the public water supply system. The public water supply system used as an auxiliary water source may be connected only to the water storage tank and may not be connected to the plumbing of a structure.
(b-4) A municipally owned water or wastewater utility, a municipality, or the owner or operator of a public water supply system may not be held liable for any adverse health effects allegedly caused by the consumption of water collected by a rainwater harvesting system that is connected to a public water supply system and is used for potable purposes if the municipally owned water or wastewater utility, municipality, or public water supply system is in compliance with the sanitary standards for drinking water applicable to the municipally owned water or wastewater utility, municipality, or public water supply system.
(b-5) A municipality or the owner or operator of a public water supply system may not be held liable for any adverse health effects allegedly caused by the consumption of water collected by a rainwater harvesting system that uses a public water supply system or an auxiliary water source and is used for potable purposes if the municipality or the public water supply system is in compliance with the sanitary standards for drinking water adopted by the commission and applicable to the municipality or public water supply system.
(c) Standards and rules adopted by the commission under this chapter governing public drinking water supply systems do not apply to a person:
(1) who harvests rainwater for domestic use; and
(2) whose property is not connected to a public drinking water supply system.