KENNY G wrote:its a triton hawaii 2 electric shower.
I presume you mean the water is coming from the small pipe behind where the shower hose is?
This is not an overflow but a pressure relief valve designed to protect the shower if the hose or head becomes blocked. When excess pressure is experienced, a small ball bearing is forced out allowing water to flow down the pipe
This part is supposedly non resettable so ought to be replaced. If however, you can find and replace the ball bearing it may be possible to avoid buying a new part. Of course, you need to address the cause of the over pressure in the first place.