The washer is just there so it fits properly. Unless it is a different thickness than the one that came with mine, I don't think it will cure the problem. I haven't done anything to fix the problem yet. It is almost unnoticable. It melted about the a 1/4" by 1" section on the bottom of the number plate.. Not really melted, just warped it a bit. When I get around to fixing it, I just plan to put some additional heat tape on the plastic in that section. I think that will do it. Enjoy the pipe!!