Hi Jack937, Thank you for your question!
If your 3 handle faucet is a Delta product and it was manufactured before 1990, then the RP21598 and RP10799 diverter assemblies will fit the valve body. If your 3 handle faucet is a Delta product and it was manufactured after 1990, then the RP17730 diverter assembly will fit the valve body. If you are installing the correct diverter assembly and your faucet is still not functioning properly, then the valve body itself may be damaged and it will need to be replaced.
Date published: 2016-04-22