The last one I dismantled the piston was brass, 2 parts threaded together. You might need to warm it up with a blowtorch to undo it, which will ruin the washer, but no matter if you're changing it.On new part one float vales the washer is sort of intrigated in a plastic piston. What is it like on old part one float valves? I don't think they had a plastic piston in them?
That's right, it looks like a kit for both Part 1 and Part 2. The bigger black thing is for Part 2. If you're using the plastic piston, if I remember right the washer pushes in from the side. If you re-use the brass one, unscrew it, take out the old washer, replace it and screw back together. A smear of silicone grease on the threads doesn't hurt.The middle washer in this kit looks like the part one float valve one?