I need to replace a old isolation v/v on our H.P. Receiver. The v/v is used to isolate the suction accumulator from the receiver. The question is.....is it better to pump out the plant and bring all the liquid back to the receiver which will fill the receiver to about 7/8 full then pump it down to atmospheric pressure to replace the v/v or pump all the liquid out of the receiver then blow it down?