Russell B Hattiesburg , MS January 18, 2015 Appliance: Roper Undercounter Dishwasher RUD4000MQ0 Roper Dishwasher Rud4000mq0: Water backing up into dishwasher from sink bad check valve. How to replace Collector W/Check Valve. Installed new Collector W/check Valve on the bottom of the dishwasher tub. About a 30 minute job (including removing the dishwasher from the cabinets--water supply, drain, and power--and reinstalling it. It would be nice if the manufacturer supplied the rubber check valve separately--small piece of rubber about the size of a nickel, probably $1 to $2--instead of selling it only as part of a $38 assembly. 6 People found this story helpful Do-It-Yourself Rating: Repair Time Estimate: 30-60 minutes