The top floor of my old three story house does not get any heat in the top story radiators at all. The boiler is on the ground floor and the pump is on the middle floor. I hired a power flush machine and used double the dose of cleaner and, whilst flushing with the boiler running, noticed that they did get hot when fed by the more powerful Proflush pump. Due to this, I assumed that the old 15/50 pump fitted might also need replacing, but this did not help. Could I overcome this by fitting a 15/60 pump?