a904 NSS change without draining 'trick'...

I used to replace bottom water heater elements without losing more than a quarter cup od water.

The trick is to have the new part ready to screw in as soon as the old one comes out.

Take the last few threads out on the old one with your left hand (assuming you are right handed) while you have thew one already in your right hand.

Throw or drop the old one if necessary so you can use 2 hands to thread in the new one.