Cottonwood season on the Eastside — typically late May through early July — generates one of the heaviest single-source filter loading events of the year. Black cottonwood trees (common along Eastside creek corridors and in neighborhoods near Lake Washington and Lake Sammamish) release massive quantities of white cottony seeds that enter spa filters, clog skimmer baskets, and can overwhelm the filtration capacity of any spa system.
Cottonwood seeds are the ideal spa filter destroyer — fine enough to pass through the skimmer basket but large and numerous enough to cake on the filter cartridge surface in a matter of hours. A spa that runs its normal filter cycle during a heavy cottonwood day can emerge from that cycle with a filter so coated that flow is severely restricted. The control system may show a FLO error as a result.
The practical response during cottonwood season: check and clean the filter every 2–3 days rather than weekly. Keep the spa cover closed except when using the spa — cottonwood enters the spa within minutes of the cover being opened during a seeding event. Clean skimmer baskets daily during peak seeding.
Before cottonwood, Eastside spas deal with alder and maple catkin drop (March–April) — the long, dangly flower clusters from these common Eastside trees. Catkins decompose rapidly in warm spa water and generate significant organic load for both the filter and the sanitizer. Red alder is ubiquitous in Eastside riparian areas; big-leaf maple catkins are a fixture in most residential neighborhoods. Both contribute to elevated sanitizer demand and faster filter loading in spring.
Late April through May brings the Douglas fir pollen season — the yellow-green coating that covers every outdoor surface in the Pacific Northwest. Fir pollen is fine enough to pass through most spa covers and loads filter media more efficiently than almost any other debris type. A filter that looks light yellow-green on its surface is carrying a significant pollen load. Monthly chemical filter cleaning during pollen season removes pollen that water rinsing leaves behind.
Given the Eastside's year-round organic loading — winter rain debris, spring catkins and pollen, summer cottonwood, fall leaf drop — Eastside spa owners benefit from a filter cleaning schedule tied to the season rather than a fixed interval. Heavy debris periods (April–May pollen, May–June cottonwood, October–November leaves) require more frequent attention. Light periods (February, August) may allow longer intervals between cleanings. Monitor the filter visually and by the spa's performance — reduced jet pressure is the first sign of filter restriction.
Cascade Spa Repair services hot tubs across Kirkland, Bellevue, Redmond, Sammamish, Bothell, Woodinville, Kenmore, Issaquah, Newcastle, and Mercer Island. Fixed quote after diagnosis. Call (425) 832-8476.
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