Thank you!!

Massive thanks for this.
helped me change the awkward water pump and auxiliary belt today after the water pump belt snapped and overheated the engine on the motorway, requiring recovery.
hopefully HG isn't damaged, but why the heck did Mitsubishi use a puny 3 rib belt for such an important part as the water pump?! Could have been catastrophic.

The serpentine belt should be replaced every 50-75k in any vehicle. It's not expensive and is a normal wear item. Be VERY thankful that Mitsubishi uses a timing chain in their engines. Otherwise every time you replaced the timing belt along with the tensioners and pulleys you would also replace the water pump because in those type of engines the water pump is located inside the timing belt housing and it is a very expensive maintenance item +$500 a pop. You can't let the timing belt get wet either because it will destroy the belt which is the reason why you should replace the pump every time you replace the timing belt.

Fortunately Mitsubishi uses a timing chain that will last for the life of the engine and 99.9% of all owners will never have to mess with it which saves you thousands of dollars over the life of the vehicle. So yes, the water pump is driven off the serpentine belt, that's a gift not to be overlooked.