Different Mansfield anti-syphon outdoor faucet leak
I also have the Mansfield 500 series wall hydrant. Mine just won't shut off completely. It still has a significant dribble (small stream?) coming out the normal place (it does not come out the cap or knob). It slows down the tighter I turn the knob but never completely shuts off. I have replaced all the stem items (seat washer, back flow washer, bibb washer, screw, o-rings, packing, bonnet) twice with the correct replacement kits. Also turned the seat washer over. Also tryed using stem from different faucet but same thing. Then I bought a new 12" complete stem with same results. The only thing I noticed is on the seat washer there ends up being some very tiny teeth marks. All of this tells me the problem is in the seat 12" back in the tube. I cannot replace the entire thing as it is soldered in and behind finished off downstairs room/ceiling (which I don't want to destroy). I temporarily just have a ball cock shut off valve attached to it which works but I'd like to fix the real problem if possible (especially since winters are cold here in Mn and don't want to leave water in the tube). I tryed inserting a long screwdriver and scraping off the seat. The remains of what looks like a black bib washer came out but the identical problem is still there. Does anyone have any suggestions? Also what is the shape of the seat back in the tube? Does anyone have any pictures/diagrams or even just describe it? Thanx.