I cannot find a valve to shut off my constantly running toilet, till the plumber can arrive. Every other place I've lived has had a separate shutoff valve for each toilet, sink, etc. I've looked in, under & around the back of the tank, but there is no valve on the pipe in the bathroom. I've also traced the pipe down to the basement, no luck. For now I will have to shut the main valve to the house off and on as needed (it's winter) or let the thing run. Please help!