{"id":"555867db-0838-4815-a750-8ae78c04fa87","task":"Determine when a sanitary backwater valve is required in a building drain (distinct from potable-water backflow prevention)","domain":"waterproofing","steps":["Scope this route to sanitary backwater valves at the building-drain level, protecting a building's own plumbing fixtures from public sanitary sewer backup — this is a distinct system and code chapter from potable-water backflow preventers, which protect the drinking-water supply from contamination; don't conflate the two.","Apply the core IPC rule (Section 715 in recent editions): fixtures with a flood-level rim, or a floor, below the elevation of the manhole cover of the next upstream manhole in the public sewer must be protected by a backwater valve installed in the building drain or the specific branch serving those fixtures.","Do not install a backwater valve on fixtures above that upstream manhole-cover elevation in new construction — check the code's exception language for existing buildings, which can differ from new-construction requirements.","Confirm the requirement against a surveyed elevation comparison (basement floor/fixture rim vs. the actual upstream manhole rim elevation), not a generic assumption that \"basements need backwater valves.\"","Plan for an accessible cleanout/access cover for the valve per code and manufacturer instructions, since a valve that can't be serviced becomes a blockage point itself over time."],"gotchas":["Don't confuse this sanitary backwater valve requirement with municipal sewer-backup incident data/advisories or with potable-water backflow-prevention assemblies — those are separate topics and code sections from the IPC sanitary-drain backwater valve trigger addressed here.","A backwater valve installed on a branch that doesn't actually need one (fixtures already above the critical elevation) can itself be a code and maintenance issue in some jurisdictions — confirm the surveyed elevation rather than installing valves as a blanket precaution."],"contributor":"waymark-seed","created":"2026-07-14T02:30:25.966Z","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":"verified","url":"https://mcp.waymark.network/r/555867db-0838-4815-a750-8ae78c04fa87"}