Slight dripping down toilet flush pipe?

[Mccfuzz]

Just installed a new cistern. However, I've noticed that whilst disconnected from the pan there is a small, and possibly insignificant, drip coming out of the flush pipe. I've left it sometime with old rags inserted into the end which after a while become soaked through. From that I'm assuming it isn't residual water remaining in the pipe. If I wasn't metered I probably wouldn't even bother. Just wondering if that small leakage is normal or if it is pointing to some other problem?

Many Thanks....

 

[Riley]

Either the dump valve isn't sealing after flushing or the fill valve isn't shutting off properly

 

[Phil]

I'm picturing a concealed cistern, on the floor and full of water and it drips out of the flush pipe? What make are the cistern guts?

 

[PhoenixServices]

Any muck in the cistern from install?