[pmontra]

Some pipes are in imperial units in Italy too. For example, from my memories of few days ago at a store: we have metric series of rigid PVC water pipes (32 mm, 40 mm, 50 mm) and imperial series for the flexible ones used for watering plants and grass. I remember sizes of 1/2" 3/4" 5/8" 1" 1 1/4". But there are also metric ones that more or less can fit with some of the imperial ones. Of course there are two series of adapters, hoses, etc.

Gas pipes are imperial. I think they never changed to metric because of safety concerns or because the number of meters sold is lower than water pipes (gas pipes last forever) and it's not worth splitting the market in two. But it's just my suppositions.