Watering is important not only in the amount of water the marijuana plants will receive, but also in the quality of the water. The cannabis plant will not be able to adapt to the chemicals that are used in city water and with most growers living in areas where they do not have their own personal well, but instead are provided water by the city it has chemicals. These chemicals include chlorine, this however will dissipate if left in an open container for twenty-four hours, so by letting water that will be used on the plants sit for one to two days it will be safe for the plants. Another thing that allowing the water to sit will do is bring the water to room temperature, this means that it will not cause the pot plants shock when they are watered like it would with colder tap water.

Another thing that can be done easily is to purchase anti-chlorine drops at a pet store that is used for aquarium water, this will neutralize the chorine and it will then be safe for the weed crop.  
The actual watering of the plants is important and it should be done so that the soil is evenly moist and moist all the way to the bottom of the plant, this means for a five gallon planter filled with soil it can take as much as three quarts of water. The reason that the grower must ensure that the water is reaching all the way to the bottom of the pot is that if it does not then the roots are not getting the needed amount of water it needs for the plant to grow.  Then they will begin growing in the direction of the top of the pot where they can acquire the needed amount of water.

It is also important for the plants to have proper drainage, and the best way to ensure this is to make sure there are holes in the bottom of the planters. This allows extra water to drain out of the planter and if this water could not escape it in time could cause the roots of the cannabis plants to rot, or cause other disease in the plants. Standing water in the pot can also allow mold or mildew to form, which will contaminate the plants and cause disease. This is why it is important when preparing the soil that it is mixed with sand and pearlite or sponge rock, which will allow proper drainage. The pearlite or sponge rock allow for drainage and keep the soil from clumping and clogging the holes in the bottom of the pot, while the sand helps to retain moisture.

Testing the soil for moisture is easily done, putting a finger in the soil will tell if the soil is moist and when it is moist on the top then it has even more moisture down in the pot where the cannabis roots are nourishing the plant. As a rule, the marijuana plant will handle dry better than it is able to handle extremely wet soil.