I would like to instal a pump into a simple gravity fed hot water system running from a wood burning stove with a back boiler ( output 5Kw). The system works very well at present heating water via an indirect cylinder. I would like to incorporate two small towel warming radiators into the circuit. Can I simply insert a small pump into the hot feed from the boiler with a manual on/off switch? With the pump switched off will water still circulate by convection, i.e. through the pump and through the indirect heating coil in the cylinder?