a couple of months ago i replaced a burnt out heating element for my immersion heater ,well today no hot water , the timer is ok but the element is not heating up, so i assume its knackered , the thing is its a "BACKER" element and i wonder if anyone has had any problems with this brand ,when i installed it and turned it on it seemed to vibrate, now thats not normal is it . i can`t find the reciept do you think they`ll replace it............the last time i change the immersion tank and element was about 10 years ago............thanks..................