New Mansfield flush valve seal

Discussion in 'Toilet Forum discussions' started by punkyb76, Jun 30, 2007.

  1. punkyb76

    punkyb76 New Member

    Jun 30, 2007
    Hello experts,
    I recently identified that all of the toilets in my house are in need of flush valve seal replacements. It is clear that these seals are eroded and brittle. I have replaced the valve seals with new ones. However, the new valve seals seem to be stiff and do not make a tight seal with the plastic "cup" that comes down over them.

    I noticed that the older valve seals were no longer flat and instead have conformed to the shape created between the plastic cup and the bottom of the tank (kind of like the rim around the edge of a plate). The new valve seals are completely flat and are stiff (being new). I believe that they need to be softened up a bit to create a better seal, but this is only a guess from a novice plumber (namely, me).

    I would be extremely appreciative if anyone has an tweaks to make the new seals form a nice, tight seal.

    ...and thank you to all of the experts who even take the time to read this, let alone offer a suggestion.

    Thank you,
  2. Verdeboy

    Verdeboy In the Trades

    Jun 12, 2006
    How does the bottom of the "plastic cup" look? If it is deformed, you will never get a good seal and will have to replace it. If it is not deformed, try using a little force to push down on the plastic cup a few times to try to get it to seal. If it still leaks, try using a new gasket until you get one that doesn't leak.

    Now you see why many of us prefer to use the flapper ball type flush valve.
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  4. Cass

    Cass Plumber

    Nov 12, 2005
    Do you have the new style that is just a red or gray ring or do you have the old style?

    If the ring (new style)is installed properly it will spin / turn smoothly in the groove holding it in place. Many times people install it below the groove that it should be in.

    Remove the cup and inspect where it comes in contact with the ring and see if there is any mineral build up on it. Run a wet finger around on it a few times and feel for any roughness.
  5. punkyb76

    punkyb76 New Member

    Jun 30, 2007
    problem solved

    Cass - Thanks for the reminder. I actually read the directions and I did make sure that the ring was set into the top-most groove on the vertical plastic cylinder. It's amazing what can be done with actually reading directions! Thanks again.

    Verdeboy - Yes, I will definitely be replacing them with the flapper-type seal when major work comes around. This Mansfield system seems "cheap and easy."

    And just FYI, I did come up with a solution. I noticed that the new rubber valve seals were good but stiff. To fix the problem, I pushed down on the vertical, moveable plastic piece to force the rubber to make a proper seal. Then, I simply left the good seal like that in place for 48 hours without flushing the toilet. The rubber seal seems to have softened up a bit and now maintains a good seal between flushes.

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