Rainwater Harvesting

By Russell Hamilton, Executive Director

For years people have been collecting and using rainwater for irrigation purposes and as a potable water source.  The last legislative session passed laws that allow for individuals to construct systems and utilize rainwater as a source for potable water even within the jurisdiction of a city or Public Water Supply (PWS).

TCEQ is currently accepting comments regarding rainwater harvesting. All comments should be directed in the form of an email to Cindy Haynie – This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Concerns might be that when you have a known water supply connected to an unknown water supply you have by definition a cross connection.  Proponents of rainwater harvesting take the stance that a rainwater harvesting system should be considered no different than a private well.  Counter to this line of thinking is that typically in a rural setting, if a house or business has a private well they are not also connected to a Public Water Supply (PWS).

If the rainwater harvesting system is connected in any way to the PWS there exists a possibility for cross contamination.  One obvious requirement is to require a RPZ at the meter connection, but is that enough for the protection of a PWS system?  Should there be a requirement for an air gap at the point that any supply line connected to a PWS that is in turn connected to a rainwater harvesting holding tank (typically used for supplemental water, should use exceed capacity of the rainwater system)?

All of the following questions are posed with the implication that the rainwater harvesting system is being used as a private potable water source.

• Should there be requirements for the rainwater harvesting system for those who use the water for potable water (such as minimum standards for the material used)?

• Who should be authorized to design and install the system?

• Should the rainwater harvesting system require a customer service inspection from the entity and/or PWS?

• What, if any, annual inspection process should be performed on a potable rainwater system and by whom?

• What materials are considered acceptable for the roofs or rain collection area?  Proponents of the rainwater systems say anything but wood.

• Should there be automated diversion valves for wastewater at the beginning of a rain event or when the systems holding basin is 95% full?  Should it be time or volume based?

• Testing - Should the rainwater system be required to submit bacteriological samples and source water samples?  If so, how often?

• If the rainwater harvesting system is located within an entity that has a plumbing code that provides oversight, what rule supersedes?  Local plumbing code, TCEQ, etc.

• Should there be some type of requirement for filtration and/or disinfection?

• Should rainwater harvesting systems located within an incorporated area have the same requirements and stipulations as one located on a farm or ranch outside the incorporated area?

• Should there be some requirement for signage or posting so that any guest or non permanent habitant of the house or business that is using rainwater as a potable water source know without asking that the water used inside this structure is not from a PWS?

• Should there be rules and requirements for disinfection of the holding basin and any piping with 50 mg/L chlorine?  If so, what about de-chlorination and disposal of the waste?  Should this act require the supervision of a licensed operator or should a plumber be required to attend additional training and obtain some type of endorsement from the state?

• Should there be a rule or requirement for disinfecting the collection area (roof) before placing the system in service, if the system is used for potable water?  Should there be a rule or requirement for annual disinfection of the collection area if the system is used for potable water?  Should gutters, downspouts, and any piping require this same disinfection?

• Should there be a minimum requirement for square footage of the collection area?  If so, should the collection area be tied to a reservoir size or holding basin minimum size requirement?

• Should there be any notification requirements to an entity and/or PWS related to the entity or PWS’s sampling and monitoring plan?  Basically what, if anything, should be required so that a PWS does not mistakenly use a newly installed rainwater harvesting system as part of the monthly bacteriological monitoring requirements of the PWS?

• Should a licensed irrigator or water treatment specialist be approved to make any installations or connections of a rainwater harvesting system that will be used in a potable water setting?

If this rainwater harvesting topic is of any interest or concern, you are urged to use this time that TCEQ has open for comments and input to make the state aware of your concerns or support.