The pipe leaks (very little) at the point it enters the valve ie NOT at the radiator. If tightening doesn't fix it, will I have to drain the system. The rads in that room are getting changed, and it's obviously daft to chamge them on a leaking pipe! Also, the carpet is going, in favour of wood, so again, a leak is unwanted. The pipe is 10mm Hep2O. Thanks.