Building an infinity pool in Washington State
An infinity pool — also called a vanishing edge or negative edge — is built so that water spills over one precisely leveled wall into a hidden catch basin below, making the surface appear to merge with the view beyond it. Around Puget Sound, where so many properties look out over water, lakes or the Cascades, it is the feature that makes the most of a view lot — and the most engineering-intensive detail in custom pool construction.
The edge itself is a dam. A vanishing-edge wall is structural concrete built to a very tight tolerance, because water has to sheet evenly over its full length — a wall even slightly out of level reads as a dry patch. Below it sits the catch basin, sized to hold the water in transit plus the surge from swimmers and wind, with a dedicated pump returning water to the main pool. On the sloped lots where infinity edges belong, that wall often doubles as retaining structure, which is why the engineering happens before anything else.
The best candidates are sloped lots with something worth aiming at: Puget Sound, a lake, a valley or the mountains. The edge is oriented toward the view, and the drop on the far side is what hides the basin and sells the illusion. Finishes matter more here than on any other pool — a dark interior and glass or porcelain tile sharpen the mirror effect that makes the edge read from the house.
An infinity edge adds real cost — a second engineered wall, the catch basin, an additional pump and the controls to run it — which is why vanishing-edge projects sit toward the upper end of custom pool budgets. In Western Washington, plan the heater and automatic cover early so the pool is usable year-round; both need to be designed around the edge wall rather than added later. And bring the builder and engineer to the site before the landscape plan is fixed — a vanishing edge done right disappears, and the structure has to lead.
