help,problems with economy 7 heating and shower?

hello,my storad heater in living room will not work unless i put on the fast heat one hour switch.do i have to use this switch every time? if i turn off the fast switch the heater loses all heat and does not store.also my triton shower now takes several minutes to put out hot water.i assume the two problems are linked.the instruction manuel for the heating does not help.ps the heaters are ok elsewhere..