That depends entirely on your house. Many basements never flood.
That would be your flush valve in the tank
Install a one way check valve in the line from the house to the sewer.
check at a plumbing supply , for this, [ball check ] i also have had good louck by pushing a Tennis ball in to mine then replacing the top plate. Acts like a stopper,
I am facing this same issue with a basement installation and plan to use a backwater swing check valve, available thru McMaster-Carr on the web.
If carb, the float valve is stuck open. Take air horn off carb and check.
To prevent water from coming up the basement drain, you can install a backwater valve. This valve helps to prevent sewage and water from flowing back into your basement during heavy rain or flooding. Regular maintenance and inspection of the valve can help ensure it is working properly.
Install a Backwater valve
A dual check valve is similar to a double check valve in that it is a mechanical backflow preventer consisting of two independently acting, spring-loaded check valve.
Converter relief valve ensures high line pressure does not flood/overrun the solenoid.
If you've already double checked to make sure it's turned the right way, you could have a faulty valve,
To install a sump pit in a basement for effective water drainage and flood prevention, follow these steps: Choose a suitable location in the basement for the sump pit. Dig a hole for the sump pit and ensure it is deep enough to accommodate the pump. Install the sump pump in the pit and connect it to a power source. Install a check valve to prevent water from flowing back into the pit. Connect the pump to a discharge pipe that directs water away from the foundation. Test the sump pump to ensure it is working properly. Regularly maintain and check the sump pump to prevent any issues.
There is no difference between check valve and NRV, both are same