How you approach a large number of staff not washing their hands after going to the toilet?

A bit of a weird question I know.

I own a company with around 100 workers and most are men. On the workshop floor we toilets akin to a service station where it’s a little corridor and then splits to a Y with the mens on the left and the womens on the right with a doorless opening and then each has 10 cubicles and the mens has a urinal as well.

A couple of months ago I was approached by two members of staff who said every time they go to the toilet whoever else is in there doesn’t wash their hands and they don’t like it as well all touch door handles etc. I put signs up and that’s it. They approached me again two weeks ago saying it hasn’t made a difference.

Every morning since for an hour I sit at the workshop managers desk which is within hearing distance of the toilets. I have noticed that a good 50-75% of the time men go in there you cannot hear the tap running.

I don’t really know how to approach this. We don’t work in the food industry we manufacture tools and equipment and post them out. They also wear gloves for 90% or the workday.

Any help would be appreciated. Thank you.