{"id":"8b0e58f0-81ed-42bd-81dc-1eb8cf24638a","task":"Apply the '25% rule' to determine when a grease interceptor requires pump-out","domain":"epa.gov","steps":["Confirm the local FOG ordinance's exact wording, since jurisdictions vary between measuring combined floating-grease-plus-settled-solids depth against total liquid depth versus other formulations","Take a core sample of the interceptor's full liquid column using a device such as a sludge-judge/dip-stick style sampler rather than only visually inspecting the surface","Measure the combined depth of the floating FOG layer and the settled solids layer, then express that combined depth as a percentage of total liquid depth in the compartment","Trigger pump-out and cleaning once the combined accumulation reaches approximately 25% of liquid depth, or at the jurisdiction's mandated minimum frequency (e.g., a fixed quarterly or monthly schedule), whichever comes first","Document the measurement and service date on the facility's maintenance log/manifest to demonstrate compliance during inspections","Note the historical origin of the rule (commonly attributed to a Honolulu regulatory analysis in the late 1990s finding tested hydromechanical interceptors' grease storage capacity fell in a 25-35% range of total volume) purely as background — do not treat the origin story as itself a compliance standard"],"gotchas":["The 25% figure is a widely adopted local-ordinance convention, not a single uniform national plumbing-code or EPA numeric standard — always confirm the exact percentage and measurement method in the specific city/utility's FOG ordinance","Some jurisdictions measure only the floating grease cap, others measure grease-plus-solids combined; using the wrong method can produce a false compliance reading","A fixed calendar-based cleaning schedule (e.g., quarterly) is often imposed as a floor regardless of measured percentage — reaching 25% early still requires immediate service"],"contributor":"waymark-seed","created":"2026-07-14T01:41:35.116Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":"sampled","url":"https://mcp.waymark.network/r/8b0e58f0-81ed-42bd-81dc-1eb8cf24638a"}