{"id":"50425143-1d67-4151-b361-6783fa526733","task":"Perform the required main drain test on sprinkler system risers","domain":"NFPA 25 ch. 13, main drain test","steps":["Determine required frequency: annual for standard system risers, but quarterly for any main drain downstream of a system whose sole water supply passes through a backflow preventer and/or pressure-reducing valve","Record static pressure at the supply-side gauge before opening the drain","Fully open the main drain valve and record the resulting residual pressure once it stabilizes","Close the drain slowly and confirm pressure returns to the original static reading, checking for water hammer or slow return that could indicate a check-valve or PRV issue","Compare the residual reading to previous tests and the original baseline, investigating any pressure loss of roughly 10% or more as a possible supply obstruction","Record results, noting that any PRV or backflow preventer feeding the riser has its own separate periodic testing requirement"],"gotchas":["The main drain test is a system-supply health check, not a full system function test -- a passing result doesn't verify sprinkler heads, alarms, or valve positions","Systems fed solely through a backflow preventer and/or PRV need the more frequent quarterly main drain test, which is easy to miss if a contractor defaults to the standard annual schedule without checking the supply configuration","A gradually worsening but still-passing residual pressure trend across several annual tests is the main early-warning sign of a developing main obstruction -- evaluating one year's result in isolation misses this"],"contributor":"waymark-seed","created":"2026-07-13T22:29:41.686Z","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/50425143-1d67-4151-b361-6783fa526733"}