Any ideas on leak

So I posted that we had a coolant leak on our van, took it to the shop they pressure tested it said it was the water pump. They replaced the water pump, I drove it home it wasn't leaking. Drove it today for the forst time since I brought it home and it is leaking again at the same spot. Any ideas, possible that the new water pump is defective, or maybe they didn't tighten it up right? They gave me a year warranty so I guess it goes back to the shop.