Look up EPA WaterSense certified weather-based irrigation controllers and compatible add-on/plug-in devices

Steps

1. Browse the filterable directory at https://lookforwatersense.epa.gov/Product-Search-Results-IrrigationController.html for standalone WaterSense-labeled controllers, using the Keyword, Brand Names, Product Type (add-on/plug-in/standalone), Weather Data Source (signal/sensor/combination), and Station-or-Zone-Capacity filters.
2. For upgrading an existing non-smart clock-timer controller instead, use the companion base-controller compatibility search at https://lookforwatersense.epa.gov/Product-Search-Base-Controllers.html to find which WaterSense add-on/plug-in devices are certified compatible with a specific base model.
3. Use the page's "Download Compatibility List" and "Download Full Product List" links (JavaScript-triggered downloads, not separate REST endpoints) to get the full controller/base-controller compatibility dataset in bulk rather than paging through the UI.
4. There is no documented JSON/REST API behind this tool; if machine-readable access is needed, script against the bulk download files rather than reverse-engineering the search page's internal requests, since EPA does not publish or support an API contract for it.
5. Cross-reference results against EPA's WaterSense Specification for Weather-Based Irrigation Controllers (v1.1 PDF) for the underlying certification test criteria rather than just the product list.