When does a basement window well require weeping tile?

I have a seven year old bungalow in Gatineau with poured concrete foundation. The builder installed three basement windows, all a few inches below grade, so all with window wells. However, only one of the three window wells has a drain (4" tube into the ground) that I assume leads to the weeping tile under ground. I want to install a fourth window on the same side of the house as the window with the drain. I will need to get the foundation cut to accomodate the new window and I will have to put in a window well because the window will be a few inches below grade. My question is, is it necessary to have 4" drain to the weeping tile in this new window well, if one well already has it and the two other basemetn windows do not have a drain? or...when do you need to put in a drain and when is it not necessary?

Thanks