i am doing my house up slowly! and am also thinking about having a towel rad in the bathroom - i will have to alter the pipework and drain the system to at least below first floor level to do this. my question is: when re-filling a system is it very possible to get airlocks? and if so are they easy to rid? i know HOW to drain a system but any tips on re-filling would be very useful and i would be appreictative for any. I have rads on both floors, a pump and a manual air vent tee'd off the primary flow to the HWSV.