Plumbing

BuildingWrench repair guide

Plumbing

Backflow Preventer Discharging Water: What Facility Staff Should Do

Water coming from a reduced-pressure backflow assembly needs investigation. A discharge opening performs a protective function; closing that opening is not a repair.

Last reviewed 2026-09-15 · General facility-maintenance information, not a substitute for site procedures, manufacturer instructions, codes, or qualified professional judgment.

Ask Steve About This

Safety boundary

Never cap, plug or restrict a relief discharge. Do not adjust internal checks, open test cocks or isolate a fire-service supply as a general maintenance experiment.

What to check first

Bring these

  • Flashlight
  • Wet-floor signs and barrier kit
  • Water leak alarm

Step-by-step procedure

  1. 1Protect accessKeep occupants away from discharge and electrical hazards. If water is spreading, contact the building lead immediately and call the plumbing/backflow service provider.
  2. 2Identify the assemblyFrom normal access, record its make, model, size, service label and visible test tag. Confirm whether it serves domestic water, irrigation or fire protection before anyone considers isolation.
  3. 3Describe the dischargeRecord whether it is a drip or sustained flow, when it began and whether a supply interruption occurred. Do not cycle valves to reproduce the event.
  4. 4Check surrounding conditions visuallyReport a blocked receiving drain or damaged air-gap fitting without obstructing the assembly outlet. The Watts 909 reference below applies to that series, not every installed assembly.
  5. 5Arrange qualified testingA trained backflow technician should diagnose and test the assembly using the correct instructions. Document repair and any required retest before treating the event as closed.

Leave a useful maintenance record

Record the exact location, observed condition, time, actions taken, person contacted and follow-up owner. Keep unresolved items visible. A completed checklist means the check was performed; it does not automatically mean the equipment passed or is safe.

References and further reading

Watts: Series 909 / LF909 installation and maintenance instructions — https://www.watts.com/dfsmedia/0533dbba17714b1ab581ab07a4cbb521/23409-source/638748128830000000/0834246-rp-is-909s-pdf.pdf Use the installed equipment manual and your site plan for equipment-specific procedures.

Stop and call a licensed professional when

  • Continuous flow, possible contamination, an unidentified service or any fire-protection impairment requires urgent coordination with the responsible specialists.

Parts for this repair

Flashlight

Listed on the website guide for this repair.

Check on Amazon

Affiliate links — BuildingWrench may earn a commission at no extra cost to you. Verify model, size, rating, and compatibility before ordering.

Tools for this work

Full kit

Related guides