If I have an open vessel of water with a small drain hole in the bottom, what size does the hole have to be in order to overcome surface tension and allow drainage?

All of the references on surface tension will talk about capillary action, but how can I translate that theory to this problem? If the drain tube is pointing down, will the meniscus still be concave as it is in a vertical capillary?

Somehow the answer depends on the height of the water, the atmospheric pressure, and the contact angle between water and the material. In this case I am interested in plastic, so the contact angle is less than 90deg.