Agree with the other answers. Most likely the solenoid. You can buy direct from the manurfacturer or arrange for a fixed price service by ringing 0844 571 5000
Rob
June 2010
solenoid valve diaphragm is failing or grit in it causing to not to shut fully.
retail at about £35
hi-spec plumbing & heating (essex)
June 2010
sounds like the solenoid may be jammed, or the heater tank scaled up, if it is the tank then you need a new shower, if it is the solenoid they can be obtained from National shower spares. www.showerspares.com tel
0845 126 4141
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix baths and showers.