If you are telling us that your shower head leaks when the shower is running then the new shower spray head you have fitted is simply not sealed in correctly – try using hemp and a little graphite grease on the thread instead of teflon tape.
If the shower head is dripping when the shower mixer is turned off then that is another matter completely and the problem could lay with some grit or lime under the control valve seat or simply a worn out shower mixer which would need to be replaced.
Selgas Services Ltd
Craftsman Gasfitters, Plumbers, Electrical Service Technicians