Sealing a ceramic cistern on a toilet?

[ericmark]

The nut on the copper pipe to plastic is solid, but leak is past the plastic ball valve bit, can't remove to fit new rubber washer, so how can I stop the leak, I know with the Pontcysyllte Aqueduct they use sand or dirt sprinkled on inside where leaking, as it is fronded on to use ox blood today, so is there a trick to stop a toilet cistern leaking?

 

[polesapart]

Very much fronded upon to use oxblood today, except in certain Mithraic initiation rituals.
Edit - i'm wrong here ; the followers of Mithras slaughtered bulls for sacrifice, not oxen.



Replacing the ballvalve is probably the simplest and best solution.