Hello and thanks for using this service, if you have been waiting do not worry or get upset I am just one of the techs on here and I try to get to as many customers as I can and I just picked up your question now. Please give me time to respond sometimes I get your replies late so there may be a delay in my response.
Whirlpool uses a flow meter that detects the flow of water entering the washer. If this flow meter does not detect the correct amount of water entering the washer it will sound the F20 error code. Often this repair can be made with out calling an appliance repairman and without ordering parts. Start by removing the washer fill hoses; both the cold and the hot water hoses. Check for proper water pressure from the house. To do so, turn the water on and put the hose inside the washer or a bucket.
If water pressure is good, check the water valve inlet screens. Most residential washing machines have inlet screens. The screens prevent minerals from clogging the solenoid. With the hoses removed, you can visually inspect the water inlet screens. If the water valve screens are clear the inlet valve with the screens itself will need to be replaced. To replace the water valve, remove the top of the washing machine. Three screws hold the top down. The screws that hold the top down are on the back of the top panel. Once removed the top will slide back and off. Now remove the wire harness that connects to the valve. One screw holds the valve to the washers cabinet. Removing the screw and sliding the valve over will release the valve from the back panel enabling you to complete your repair.
One last thing to check is the fill hoses. These front load duet washers call for a lot of water quickly. So if you have stainless steel braided flood-safe hoses, they will trip for no reason at all. Replace these flood safe hoses with more traditional hoses.
If all that checks out ok you likely have a defective CCU board.
We are on the honor system for our time, all I ask is please rate my service using the STAR RATING LINK on your page before you leave. If you are not happy with the service please let me know before leaving a negative rating. This is the only way I am paid or credited through the site for my time. This will also allow you to get directly back to me for FREE follow up questions and tips are greatly appreciated! Thanks