Don S Salem , UT May 03, 2020 Appliance: Whirlpool Undercounter Dishwasher DU1055XTSB2 Whirlpool Dishwasher Du1055xtsb2: Wouldn't drain. How to replace Dishwasher Check Valve. This was on my mom's dishwasher it wouldn't drain. So I installed a new drain pump, check the cable, and water level switch. Then she tells me that the problem started after the new disposal was installed..... Well, the person who installed the disposal didn't drill out the plugin the disposal so check that first. 4 People found this story helpful Do-It-Yourself Rating: Repair Time Estimate: Less than 15 minutes