Wow, it seems that the rubber seal (seat) is not being fully pressed down (or not staying fully down) in its proper position on top of the spring.
Make sure that the spring is right-side up (narrow end up) and that the retainer nut is fully tightened, to hold the stem all the way down.
Secret tip- use plumber's grease (petroleum jelly, in a pinch) to lubricate the seat and bottom of stem and threads on the retainer nuts. That will help the bottom sealing surface of the stem glide smoothly over the seat without catching on it. On the nut, it will help ensure you truly have it screwed down all the way.
Answer from Jimmy Fix-it on Stack ExchangeIโm not a plumber but Iโm usually handy. Today Iโm stumped. I underestimated how over-engineered delta stuff is.
The faucet keeps dripping.
I started by replacing the rubber gasket and spring ( picture attached ) that didnโt fix it. I replaced the whole cartridge with an original delta and the handle now moves extra smoothly but the faucet still drips.
Help! I donโt want to tear up the wall! What else can I try before having to do that?
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I have an older Delta faucet in my bathtub thatโs leaking. I confirmed is not the cartridge replaceable one, but havenโt troubleshot more from there.