You could have a faulty pressure switch or a faulty water inlet valve.
If you have to shut the water off to stop the water coming in you have a faulty water inlet valve.
If by turning the washer off the water stops you have a faulty pressure switch.
The water valve is the piece the hose screw to.
It is number 6 on the mixing valve and hoses breakdown.
The pressure switch is number 4 on the control panel breakdown.
Here is a link to your washer model SAV515DEWW. | 
