Lewis County, WA Landscaping Rules: Rainwater Harvesting (2026)

020(d), the subsection adopting the 2021 Uniform Plumbing Code, specifically extends the code's reach to rainwater catchment by including Appendix Chapter K and the ARCSA/ANSI 63-2020 rainwater catchment design standard. The section also directs installers to Washington Department of Health guidance on Rainwater Catchment Systems and to two county policies named directly in the code: the Lewis County Public Health Rainwater Catchment Policy (EH-POL-200-5) and the Social Services Interim Spring/Surface Water Availability policy (EH-POL-200-4). Practically, this means a rainwater harvesting system intended to supplement or substitute for a water supply in unincorporated Lewis County is not an unregulated yard feature; it is reviewed as a plumbing system under the adopted UPC and its rainwater-specific appendix, alongside the state Department of Health's own guidance on catchment system design, storage, and treatment before the water can be used for potable or non-potable household purposes.

020(d) that adopts the base plumbing code, a rainwater catchment installation is subject to the same Building Official permit and inspection process as other regulated plumbing work in the county, and where the harvesting system interacts with an on-site sewage system or spring/surface water source, the county's Public Health and Social Services rainwater and water-availability policies govern the technical review rather than a generic landscaping standard.