Thank you for your question, and I am sorry to hear that you are experiencing a leak from your Delta 155-RB-DST. We recommend to clean the bottom puck on the valve cartridge assembly and retighten the bonnet nut to stop the leak. To do this, turn the water off at your shut off valve. Remove the handle. Unscrew the bonnet nut. Pull the valve cartridge out and clean the bottom puck on the valve cartridge assembly. Reinstall the valve cartridge assembly and retighten the bonnet by turning clockwise, to the right. Install the handle back on and turn the water back on. Test the faucet. If the faucet still leaks, we recommend to replace the valve cartridge assembly, RP50587.
Date published: 2018-11-06