CVPs and Central Lines

I need everyone's opinion please.

Does anyone measure central venous pressure via a water manometer? I work in a small hospital and we measure CVP via this method. I have a question regarding that. Do you leave the line attached to the distal port at all times? One nurse says to leave it attached to the distal port- if able- at all times. "It should never be unhooked". She says to add Heparin to the saline bag. Then another nurse says you can unhook it. Just hook it up when you want to measure it. Which is correct? I cannot find much information on the internet regarding this.

My next questions have to deal with Central Lines and Infus-a-ports.

I have seen a lot of different people comment on the non-use of Heparin Flushes. Any comments. We flush central lines and infus-a-ports, when not in use, every 8 hours with 10ml of saline and 3-5ml of Heparin Flush. Is this how everyone else does it? Also, when you are blood sampling; do you always flush before you get your sample: 1. Flush with 10ml, then waste 10ml, then draw your sample, then flush with saline, then heparin? Of course with TPN, you would flush before. I was taught in clinical, in nursing school, to 1. Draw back and discard 5ml, then your sample. I was never taught to flush prior to blood sampling; unless with TPN. Any thoughts? Thanks for you assistance.