it may be just the shower delivering fluctuating temperature not the whole hot water system, clarify this first, if it is a thermostatic shower you can replace just the cartridge if you identify the right model if its the whole hot water system put as much detail about the system and problem as possible and i will get back to you
j p lewis plumbing and heating fleet
February 2010
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.