San Mateo, CA Landscaping Rules: Rainwater Harvesting (2026)

10572. Nothing in this part shall be construed to do any of the following:

(a) Alter or impair any existing rights.

(b) Change existing water rights law.

(c) Authorize a landscape contractor to engage in or perform activities that require a license pursuant to the Professional Engineers Act (Chapter 7 (commencing with Section 6700) of Division 3 of the Business and Professions Code).

(d) Impair the authority of the California Building Standards Commission to adopt and implement building standards for rainwater capture systems pursuant to existing law.

(e) Affect use of rainwater on agricultural lands.

(f) Impair the authority of a water supplier pursuant to Subchapter 1 of Chapter 5 of Division 1 of Title 17 of the California Code of Regulations. 10573. Solely for the purposes of this part, and unless the context otherwise requires, the following definitions govern the construction of this part:

(a) “Developed or developing lands” means lands that have one or more of the characteristics described in subparagraphs (A) to (C), inclusive, of paragraph (4) of subdivision (b) of Section 56375.3 of the Government Code.

(b) “Rain barrel system” is a type of rainwater capture system that does not use electricity or a water pump and is not connected to or reliant on a potable water system.

(c) “Rainwater” means precipitation on any public or private parcel that has not entered an offsite storm drain system or channel, a flood control channel, or any other stream channel, and has not previously been put to beneficial use.

(d) “Rainwater capture system” means a facility designed to capture, retain, and store rainwater flowing off a building rooftop for subsequent onsite use.

(e) “Stormwater” means temporary surface water runoff and drainage generated by immediately preceding storms. This definition shall be interpreted consistent with the definition of “stormwater” in Section 122.26 of Title 40 of the Code of Federal Regulations. 10574. Use of rainwater collected from rooftops does not require a water right permit pursuant to Section 1201.