Me personally I just crack the line and let it depressurize that way. It's only 35-45psi. It's not dangerous, just don't let it spray in your eyes. It's only gonna spray for a second then go to a drip, there not that much volume either. I've only done a couple hundred that way so take from it what you will. Quick and easy. Don't forget to prime the system after replacement or you could end up with a few miss fires. Turn key to on (not start) position for a couple seconds a few times then start.