I replaced the shower head on my electric shower. The old one no longer gave a spray but as the rubber nozzel lining had come away from the plastic shower head, all I got was the effect of turning on a tap. The new shower head makes water pour out of the shower unit on the wall. I'm guessing due to a build up of pressure.Can I do anything? Is there a way other than hit and miss to tell if a shower head will work properly?