Bath tap runs for 15 seconds after turning off

[slowleak]

I have just fitted a Bristan Java one hole bath filler to a new bath. It runs fine without leaks (well it does now). However, when I push the single lever all the way down (to turn it fully off), it simply slows the flow, then after a few seconds it dribbles and eventually, after several seconds (say 12-15) it stops completely. ie, it takes 15 seconds to stop the water coming out.

Any suggestions as to why this might happen?

Many thanks in advance.....

 

[Nige F]

It`s a big hollow casting that traps a quantity of water...which then dribbles out slowly....bit like me on the beer