I placed a deep well on a water source, pump and tank connected, but it doesn't pump water.
A placed a regular well next to it and the water started flowing immediately.

What's strange,is that if I click on the regular well the water source overlay shows up, but if I click the deep well it doesn't.

Am I missing something here?

Edit:

Ah it seems that regular and deep wells use a different water source. I planned my construction based on the overlay that showed up while the regular well was selected.

May I suggest using a different overlay color for the deep source overlay to make it less confusing?