Scope: non-structural accessories bought alongside a pool, hot tub/spa, or sauna — cleaning tools, covers, water-chemistry testers/feeders, and sauna heater accessories (rocks, bucket/ladle, thermometer) — not the pool/spa/sauna unit, pumps, filters, heater units, or toys/floats.

## Seed
1. Equivalent of "weave over thread count": the generic trap is cover color or "number of accessories included"; the real split is the cover's ASTM F1346 label class (PSC/MSC safety cover vs uncertified "other cover") and FAS-DPD vs strip accuracy for chlorine.
2. Sommelier persona: would read sauna rock choice (olivine diabase vs peridotite) as a terroir/processing question — same rock family, different density and thermal-shock tolerance — and would check a cover's ASTM label the way they'd check an AOC, which most buyers never do.

## Sources
- [astm_f1346_coverstar] coverstarcentral.com PDF "Safety Covers and Labeling Requirements" — PSC/MSC/OC classes, 485/275 lb static load, 30-min drain — fetched PDF text (pdftotext)
- [activepoolsupply_astm_f1346] activepoolsupply.com/pages/is-my-pool-cover-a-safety-cover — three label classes, 485/275 lb load, clause 8.12 labeling — fetched excerpt
- [katchakid_astm_f1346] katchakid.com astm-standard-f1346-91 page — 485/275 lb load, 30-min surface drainage test — fetched excerpt
- [intheswim_mesh_vs_solid] intheswim.com blog mesh-vs-solid-safety-pool-covers — mesh drains via panel/pump, minimizes but doesn't block all sunlight — fetched excerpt
- [royalswimmingpools_mesh_vs_solid] blog.royalswimmingpools.com safety-cover article — tight-weave mesh blocks ~99% UV; solid blocks sunlight entirely — fetched excerpt
- [backyardalpha_solar_thickness] backyardalpha.com best-pool-solar-cover-thickness — 16 mil thickness and heat-retention framing — fetched excerpt
- [patchpilotry_solar_12v16] patchpilotry.com 12-mil-vs-16-mil solar cover comparison — 12 mil vs 16 mil heat retention/durability — fetched excerpt
- [poolguardusa_winter_cover_weight] poolguardusa.com/winter-pool-cover — "8–20 oz per sq. yard (depending on thickness)" — fetched excerpt
- [heavydutytarps_material_weights] heavydutytarps.com/material-weights — vinyl/mesh tarp weight chart up to 22 oz/sq yd — fetched excerpt
- [troublefreepool_test_kits_compared] troublefreepool.com blog test-kits-compared + FAS-DPD glossary — FAS-DPD reads FC+CC direct, 0.2 ppm steps — fetched excerpt
- [poolfounder_testing_methods] poolfounder.com pool-water-testing-methods-comparison — OTO/strips total-only; FAS-DPD 0.2 ppm resolution — fetched excerpt
- [lesliespool_chlorinator_types] lesliespool.com blog three-types-of-pool-chlorinators — automatic/salt/floating taxonomy — fetched excerpt
- [intheswim_chemical_feeders] intheswim.com eguides chemical-feeders — floating chlorinator description — fetched excerpt
- [poolresearch_cleaner_types] poolresearch.com/pool-vacuums — robotic/pressure/suction differences, booster pump need — fetched excerpt
- [maytronics_robotic_cleaners] maytronics.com/us robotic-pool-cleaners — "cordless" product line distinct from corded — fetched excerpt (URL paths)
- [tfp_pool_brushing_wiki] troublefreepool.com/wiki Pool_Brushing — nylon-only on vinyl/fiberglass/resin, stainless scratches — fetched excerpt
- [poolpartstogo_brush_surfaces] poolpartstogo.com which-pool-brush-is-right-for-you — matches bristle material to pool surface — fetched excerpt
- [thermalfinn_sauna_stones_guide] thermalfinn.com sauna-stones-guide-v2 — olivine diabase & peridotite are the two sauna-rated stones; HUUM DROP spec 55kg/5-10cm — fetched excerpt
- [steamandsaunaexperts_best_rocks] steamandsaunaexperts.com/blog best-rocks-for-sauna — peridotite denser/slower heat-up than olivine; avoid porous lava rock — fetched excerpt

## Branches
- accessory_category -> cleaning_tool: "robotic, pressure, suction, or manual" differ enough to need their own facet set (poolresearch_cleaner_types).
- accessory_category -> cover: cover facets only apply once "cover" is picked; ASTM class doesn't apply to cleaners/testers (astm_f1346_coverstar).
- accessory_category -> water_chemistry_device: test_method and chemical_feeder_type are the two things that vary (troublefreepool_test_kits_compared, lesliespool_chlorinator_types).
- accessory_category -> sauna_accessory: rocks vs bucket/ladle vs thermometer are judged on unrelated specs (thermalfinn_sauna_stones_guide).
- cleaner_drive_type -> manual_pole_tool: only manual tools need bristle-material routing; power_requirement/filtration don't apply (tfp_pool_brushing_wiki).
- cleaner_drive_type -> suction_side: no separate power_requirement since it just uses the existing pump (poolresearch_cleaner_types).
- cover_classification -> other_cover_not_rated: mesh/solid routing doesn't apply to winter/solar covers; thickness/weight do instead (intheswim_mesh_vs_solid, backyardalpha_solar_thickness).
- cover_classification -> power/manual safety cover: mesh_or_solid applies; thickness/weight facets (solar/winter) don't, since those are "other cover" territory (royalswimmingpools_mesh_vs_solid).

## Noise
- Price, brand, star rating — excluded per rule (never facets).
- Cover color / cosmetic pattern — no expert consequence found.
- Cord length (robotic) / hose length (pressure-side) — install detail, not a buyer-facing split; too installer-specific to source cleanly.
- Reel system for solar covers — accessory-to-accessory, not the cover itself.
- Sauna rock quantity/weight (kg) and exact cm size — heater-model-specific per manufacturer manual (HUUM DROP: 55kg, 5-10cm); only one clean numeric source found, so left as a manual-check note rather than a sourced facet/range.
- App connectivity / "smart" features on robotic cleaners — marketing layer, not a cleaning-performance differentiator in sources checked.
- Warranty length — not expertise.
- Pool/spa shape and size (rectangle vs custom-cut cover) — a fit constraint, not a facet of the accessory's own quality.

## Corrections
- reference kinds: schema enum is standards_body/regulator/spec_sheet/enthusiast_community/specialist_review/academic/primer/retail_listing/other, not "standard"/"review"/"forum" — remapped all.
- trimmed mechanism.plain (153->150 words) and 3 cold_start_questions (13->12 words) to fit caps.

## Corrections (2026-10-26)
- Added `bucket_ladle_material` facet (wood-with-liner/metal/molded-plastic) to fix the sauna_accessory_type stub bundling `bucket_and_ladle` with no judging facet; sourced to finnmarksauna.com's bucket collection page and a product spec table showing a fitted plastic liner [finnmarksauna_bucket_collection, finnmarksauna_bucket_product_alder].
- Added `thermometer_hygrometer_type` facet (thermometer-only/combined) to fix the same stub for `thermometer_hygrometer`; sourced to two finnmarksauna.com product spec tables, one listing Type "Sauna thermometer" and one "Combined sauna thermometer and hygrometer" [finnmarksauna_thermo_only, finnmarksauna_thermo_combined].
- Reworded `sauna_accessory_type`'s why_experts_care to match what the two new facets actually cover (material/liner; temperature-only vs. temperature+humidity) instead of the unsourced "sauna-rated vs. household" framing.
- Corrected `solar_cover_thickness.range.min` from 8 to 12 mil: the cited sources (backyardalpha, patchpilotry) only ever discuss 12 mil and 16 mil products, never 8 or 10; the 8 mil floor was an invented value. Reworded why_experts_care and the visual encoding to match.
- Added `navigation_pattern` facet (random_pattern/mapped_path) scoped to robotic cleaners via cleaner_drive_type's `robotic` then_ask, sourced to poolresearch_cleaner_types ("suction-side cleaners move randomly... robotic cleaners have software that maps the pool") and a new source, swimuniversity.com's robotic-cleaner buyer's guide ("scans the pool to optimize its path... instead of relying on random patterns").
- Reclassified `winter_cover_fabric_weight.source` from "listing" to "researched": the 8 oz floor rests on one brand-style spec page (poolguardusa), and the second citation (heavydutytarps) is a generic non-pool tarp chart, not evidence the spec is on most retail listings. Could not find a second pool-specific source for the 8 oz figure within budget (web search quota was exhausted; direct curl attempts at other pool-cover retailers' winter-cover pages returned 403/404); range itself is kept since poolguardusa states "8-20 oz per sq. yard" verbatim.
- Added vocabulary entries for "Return-line pressure", "Suction line" (both cleaner_drive_type) and "Photometer" (test_method), all previously undefined but load-bearing in the mechanism/facet text.
- Rejected required-fix item 6 (lower-confidence UL 2560 check): could not re-fetch the looploc.com safety-cover page myself within this session's budget (candidate URLs 404'd; web search quota was exhausted) to independently confirm the UL language the checker quoted. Per policy, a claim isn't cited unless the fetched text was seen directly, so no UL-related facet value or judgement was added; ASTM F1346 remains the sole cited standard.