When fitting a brake (light) pressure switch into a 4 way brake union - should I fit a copper washer?

Tar,
Andy

I didn't an it's fine, I think I used a bit of PTFE tape

Rich.

I didn't fit one and it doesn't seem to leak. I think the brass is probably soft enough to form a good seal when you tighten it up.

HTH

Nick

I used a little PTFE plumbers tape for a bit of security but i think as said the copper will make a good seal.