Dripping Shower Head

[LittleJoe]

I have renovated my en-suite and fitted a new shower head and Mixer valve which is fed from a Power pump. I removed the non-return valves from the mixer valve as I had read that they weren't necessary and may reduce the pressure.
I now find that everything works fine except when I switch the shower off, after anything from 1 to 4 hours afterwards, the shower head suddenly starts dripping. This can be quite annoying when it happens in the middle of the night and I wake up thinking we have a major leak!!!
The shower head is a largish drench type head. I am thinking that there is a vacumn that prevents the water releasing from the head but after a while, this vacumn is lost and the water is released.
Could the fitting of a single check valve on the shower head fix this problem or should I refit the Mixer valve non-return valves?
Any advice appreciated.
Regards

 

[ChrisR]

They can take several yonks to empty, but if the valve isn't passing, it should stop.
I'd remove and dismantle the new valve, perhaps there's some debris in it.
Did you see/remove any filters?

 

[LittleJoe]

ChrisR,

Thanks for the comments but I should have added that it soes stop dripping after about 3 or 4 minutes. The head doesn't drip all the time.
I've never had this before where a Shower head suddenly sheds the water that seems to be trapped in the head after a few hours after a shower.