I have finally unscrewed the NRV in a Radius No 1, but the bloody thing won't fall out of its spot at the end of the pump tube, even with some gentle tapping with a mallet. It turns freely but is still down the bottom! I was considering getting a pressure pump and pressurising the tank to 'blow' it loose? Is that a mad thing to do? And what would be the maximum pressure to apply without blowing the tank?