While the valve is closed
Do not use toilets, sinks, showers, dishwashers or washing machines connected upstream of the closed valve. Water used inside cannot leave through the protected line and may back up on the house side.
After the event
Confirm the flap has reopened, check for debris, follow the manufacturer guidance and arrange an inspection if the valve does not return to normal operation.
Consider an alarm
An alarm can help notify occupants that the valve has closed, but it does not replace the device, maintenance or appropriate response.
Questions
Can I install or service the valve myself?
Backwater-valve installation is regulated plumbing work and should be performed through the appropriate qualified and licensed contractor. Homeowner maintenance should follow the manufacturer instructions and local safety guidance.
How often should the valve be checked?
Follow the manufacturer instructions and local guidance. Some authorities recommend inspection every three months, while other programs recommend at least annual or pre-storm checks.
What if I cannot find the access?
Do not assume the valve is maintenance-free. A plumber or drainage contractor can help locate the device and determine whether the access has been covered or removed.