I have never understood how this was effective against a determined adversary. An arbitrary limit like 100ml is pointless when there is no limit to the number of times you can pass through the checkpoint.
I second this. I picked up one second hand a while back. The placard indicates it was built in 1997. It needed a good cleaning and had clearly seen a lot of use, but is perfectly functional. The shower arm was showing slight signs of rust around the hole but getting replacement parts is trivial as the design hasn't changed in decades.