I have wondered this also. I have always thought that it must be on the left to make it harder for the average homeowner to work on. Having worked in bicycle shops as a mechanic for eight years before entering the construction field, and having developed ability in both the right and the left hand, I find it amusing to watch people work on the left side of the toilet with their right hand.

In other countries, the water inlets are interchangeable

Terry.

• Information on low flow toilets