Master Reg gives a simple and sure way to tell if you have a leaky fill valve that's letting water come into the drum when the washer is off. If you need water fill valve, you can buy it by clicking the picture below.

Un-plug Power Cord from Wall Outlet.

If water continues to enter, bad Water Valve.

click on picture

The hot and cold water inlet valves are located at the back of the washer.

Water Inlet Valve #1 in diagram

Source: Procedure for replacing fill valve on Whirlpool Duet GHW9150PW0