How can I get the supply line brass valve seat on Pfister tub/shower mixer valve to stop leaking?
Don't know about that particular model but I have brass seats as well. I had a leak and carefully replaced washers on both sides properly. Still had a small leak. Replaced both valve seats (only $4 each so why not) even though I knew it was clearly the cold leaking. Checked and double checked and examined seats and washers carefully -- nothing odd. Still leaked. Finally cut some teflon tape lengthwise to match the width of the threads on the seat and wrapped kinda taught 2.5 times around. Put them back in and torqued fairly firm but not overly hard. Leak was fixed.