Oklahoma City, OK Landscaping Rules: Rainwater Harvesting (2026)

Oklahoma has long recognized rainwater harvesting as a property right, and Oklahoma City encourages residential and commercial collection for landscape irrigation, toilet flushing in commercial buildings, and general non-potable uses. Residential rain barrels of 100 gallons or less connected to downspouts for outdoor irrigation require no permit and no inspection. These systems should have screened inlets to exclude debris and mosquitoes, overflow directed away from foundations, and child-safety covers.

Larger cistern systems — typically 500 gallons to several thousand gallons — require a plumbing permit if connected to any indoor plumbing fixtures. When harvested water is used indoors for toilet flushing or irrigation of commercial landscapes piped through a building, the system must include a labeled separate piping system (purple pipe recommended) and backflow prevention to ensure no cross-connection with potable supply. Potable use (drinking, cooking, showering) requires full treatment including filtration and disinfection and is rarely permitted without engineered approval. The Oklahoma Water Resources Board provides guidance, and Oklahoma City Utilities occasionally offers rain barrel rebate programs to reduce stormwater runoff. Harvested water used exclusively outdoors through hose connections or drip irrigation is the simplest and most common residential approach.