sounds like lime build up to me.shower heating unit will have to be removed and descaled using killrock or other lime busting liquid.after this your shower unit should work like its new. instructions for use of descaler will be on container . ps please make sure its perfectly rinsed out before use.while your at it also place your shower head in white vinegar or similar to clear jets from build up of lime. hope this helps GOOD LUCK.
MARK L H.POOL, June 2010
