Just for clarification, the #12 Housing gasket is a flat gasket that goes into a receiver slot in the #7 Pump/Strainer Housing. You have to pull out the old gasket and slip in the new gasket. The gasket will go most of the way into the receiver slot, but a little will be left exposed. When the pump is assembled, the #13 Seal Plate will be compressed against the exposed part of the gasket.
#7 Pump/Strainer Housing showing the gasket receiver slot.
http://www.kaboodle.com/reviews/hayward ... ound-pumps
The slot in the seal plate is not to allow water to drain out. However, I don't know why it's there.
Seal Plate
http://www.poolsupplyworld.com/poolsupp ... 2600E5.htm
The #14 Motor mounting plate contains the drain hole.

#7 Pump/Strainer Housing showing the gasket receiver slot.
http://www.kaboodle.com/reviews/hayward ... ound-pumps
The slot in the seal plate is not to allow water to drain out. However, I don't know why it's there.

Seal Plate
http://www.poolsupplyworld.com/poolsupp ... 2600E5.htm
The #14 Motor mounting plate contains the drain hole.