It is best if you do not drink water straight from the tap, even when brushing your teeth. Many people that do drink the water get sick with gastroenteritis, which is a bacterial illness found in Africa.
The good thing is that if you get sick from it once, you can not get sick from it again because you will be immune.
If you like salads, you should know that in Morocco they wash the salads in tap water. You could go a whole vacation taking precautions with the water, and eventually end up getting sick from the water on salad.
You also have to make sure when you buy bottles of water that the cap was securely sealed, because sometimes people refill bottles with tap water to make money. This can be found in low class restaurants.