Issaquah, WA Landscaping Rules: Rainwater Harvesting (2026)

LUC 18.516.040 governs the structural elements of rainwater catchment systems and other forms of micro-scale stormwater management accessory to a residential use. It sits in Chapter 18.516, whose intent clause includes providing opportunities for sustainable stormwater run-off and catchment systems on private property. The chapter's applicability section, 18.516.020, names rain and stormwater catchment systems on private property, such as rain barrels on a residential lot, as covered, and adds that the chapter does not apply to solar panels, which are regulated per Building Code.

The section sorts catchment elements into three tiers. First, no element of any size can extend into the front setback. Second, a small element, meaning one with a height of less than 54 inches above finished grade that contains up to 600 gallons, gets a limited allowance in the side and rear setbacks: it can extend up to 20 percent of the required linear distance, but no closer than three feet from the property line. Third, a system with a height greater than 54 inches above finished grade, or one that contains over 600 gallons, gets no allowance and must comply with all required setbacks. Height and volume are alternative triggers, so exceeding either one moves the system into the third tier.

The setback distances themselves come from the zone standards of the Land Use Code. For residential zones, 18.508.030(E) points to IMC 18.404.090, Residential zones form and intensity standards, for the required setbacks of minor accessory structures, so the 20 percent allowance is measured against whatever side or rear setback the lot's zone requires. The section itself prints no permit step, fee or registration requirement for a barrel or cistern. It is a placement rule, and it is enforced like any other civil provision of the Issaquah Municipal Code.